/* ==========================================================================
 * dns.c - Recursive, Reentrant DNS Resolver.
 * --------------------------------------------------------------------------
 * Copyright (c) 2008, 2009, 2010, 2012-2016  William Ahern
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to permit
 * persons to whom the Software is furnished to do so, subject to the
 * following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
 * NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 * USE OR OTHER DEALINGS IN THE SOFTWARE.
 * ==========================================================================
 */
#if !defined(__FreeBSD__) && !defined(__sun)
#ifndef _XOPEN_SOURCE
#define _XOPEN_SOURCE 600
#endif

#undef _DEFAULT_SOURCE
#define _DEFAULT_SOURCE

#undef _BSD_SOURCE
#define _BSD_SOURCE

#undef _DARWIN_C_SOURCE
#define _DARWIN_C_SOURCE

#undef _NETBSD_SOURCE
#define _NETBSD_SOURCE
#endif

#ifdef _MSC_VER
#define DNS_INLINE __inline
#else
#define DNS_INLINE inline
#endif

#include <limits.h> /* INT_MAX */
#include <stddef.h> /* offsetof() */
/*#ifdef _WIN32
#define uint16_t unsigned short
#define uint32_t unsigned int
#else*/
#include <stdint.h> /* uint32_t */
// #endif
#include <stdio.h>  /* FILE fopen(3) fclose(3) getc(3) rewind(3) */
#include <stdlib.h> /* malloc(3) realloc(3) free(3) rand(3) random(3) arc4random(3) */
#include <string.h> /* memcpy(3) strlen(3) memmove(3) memchr(3) memcmp(3) strchr(3) strsep(3) strcspn(3) */
#ifndef _WIN32
#include <strings.h> /* strcasecmp(3) strncasecmp(3) */
#endif
#include <ctype.h> /* isspace(3) isdigit(3) */
#include <errno.h> /* errno EINVAL ENOENT */
#include <signal.h> /* SIGPIPE sigemptyset(3) sigaddset(3) sigpending(2) sigprocmask(2) pthread_sigmask(3) sigtimedwait(2) */
#include <time.h> /* time_t time(2) difftime(3) */
#undef NDEBUG
#include <assert.h> /* assert(3) */

#if _WIN32
#ifndef FD_SETSIZE
#define FD_SETSIZE 2048
#endif
#include <winsock2.h>
#include <ws2tcpip.h>
#ifndef USE_FIXED_NAMESERVERS
#include <IPHlpApi.h>
#pragma comment(lib, "IPHLPAPI.lib")
#endif

#if defined(__MINGW32__) || !defined(WINAPI_FAMILY_PARTITION) || !defined(WINAPI_PARTITION_DESKTOP)
#define BELLE_SIP_WINDOWS_DESKTOP 1
#elif defined(WINAPI_FAMILY_PARTITION)
#if defined(WINAPI_PARTITION_DESKTOP) && WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
#define BELLE_SIP_WINDOWS_DESKTOP 1
#elif defined(WINAPI_PARTITION_PHONE_APP) && WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_PHONE_APP)
#define BELLE_SIP_WINDOWS_PHONE 1
#elif defined(WINAPI_PARTITION_APP) && WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP)
#define BELLE_SIP_WINDOWS_UNIVERSAL 1
#endif
#endif

#else
#include <sys/select.h> /* FD_ZERO FD_SET fd_set select(2) */
#include <sys/socket.h> /* AF_INET AF_INET6 AF_UNIX struct sockaddr struct sockaddr_in struct sockaddr_in6 socket(2) */
#include <sys/types.h>  /* FD_SETSIZE socklen_t */
#if defined(AF_UNIX)
#include <sys/un.h> /* struct sockaddr_un */
#endif
#include <arpa/inet.h>  /* inet_pton(3) inet_ntop(3) htons(3) ntohs(3) */
#include <fcntl.h>      /* F_SETFD F_GETFL F_SETFL O_NONBLOCK fcntl(2) */
#include <netdb.h>      /* struct addrinfo */
#include <netinet/in.h> /* struct sockaddr_in struct sockaddr_in6 */
#include <poll.h>       /* POLLIN POLLOUT */
#include <unistd.h>     /* _POSIX_THREADS gethostname(3) close(2) */
#endif

#include "dns.h"

#if defined(HAVE_RESINIT) || defined(USE_STRUCT_RES_STATE_NAMESERVERS)
#include <resolv.h>
#endif

#if defined(HAVE_RESINIT)
#include <ifaddrs.h>
#include <net/if.h>
#endif

#ifdef __ANDROID__
#include <sys/system_properties.h>
#endif

#include <bctoolbox/defs.h>
#include <bctoolbox/port.h>
#include <belle-sip/utils.h>

/*
 * C O M P I L E R  V E R S I O N  &  F E A T U R E  D E T E C T I O N
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#define DNS_GNUC_2VER(M, m, p) (((M) * 10000) + ((m) * 100) + (p))
#define DNS_GNUC_PREREQ(M, m, p)                                                                                       \
	(__GNUC__ > 0 && DNS_GNUC_2VER(__GNUC__, __GNUC_MINOR__, __GNUC_PATCHLEVEL__) >= DNS_GNUC_2VER((M), (m), (p)))

#define DNS_MSC_2VER(M, m, p) ((((M) + 6) * 10000000) + ((m) * 1000000) + (p))
#define DNS_MSC_PREREQ(M, m, p) (_MSC_VER_FULL > 0 && _MSC_VER_FULL >= DNS_MSC_2VER((M), (m), (p)))

#define DNS_SUNPRO_PREREQ(M, m, p) (__SUNPRO_C > 0 && __SUNPRO_C >= 0x##M##m##p)

#if defined __has_builtin
#define dns_has_builtin(x) __has_builtin(x)
#else
#define dns_has_builtin(x) 0
#endif

#if defined __has_extension
#define dns_has_extension(x) __has_extension(x)
#else
#define dns_has_extension(x) 0
#endif

#ifndef HAVE___ASSUME
#define HAVE___ASSUME DNS_MSC_PREREQ(8, 0, 0)
#endif

#ifndef HAVE___BUILTIN_TYPES_COMPATIBLE_P
#define HAVE___BUILTIN_TYPES_COMPATIBLE_P (DNS_GNUC_PREREQ(3, 1, 1) || __clang__)
#endif

#ifndef HAVE___BUILTIN_UNREACHABLE
#define HAVE___BUILTIN_UNREACHABLE (DNS_GNUC_PREREQ(4, 5, 0) || dns_has_builtin(__builtin_unreachable))
#endif

#ifndef HAVE_PRAGMA_MESSAGE
#define HAVE_PRAGMA_MESSAGE (DNS_GNUC_PREREQ(4, 4, 0) || __clang__ || _MSC_VER)
#endif

/*
 * C O M P I L E R  A N N O T A T I O N S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#if __GNUC__
#define DNS_NOTUSED __attribute__((unused))
#define DNS_NORETURN __attribute__((noreturn))
#else
#define DNS_NOTUSED
#define DNS_NORETURN
#endif

#if __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-parameter"
#pragma clang diagnostic ignored "-Wmissing-field-initializers"
#pragma clang diagnostic ignored "-Wdeprecated-non-prototype"
#elif DNS_GNUC_PREREQ(4, 6, 0)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-parameter"
#pragma GCC diagnostic ignored "-Wmissing-field-initializers"
#endif

/*
 * S T A N D A R D  M A C R O S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#if HAVE___BUILTIN_TYPES_COMPATIBLE_P
#define dns_same_type(a, b, def) __builtin_types_compatible_p(typeof(a), typeof(b))
#else
#define dns_same_type(a, b, def) (def)
#endif
#define dns_isarray(a) (!dns_same_type((a), (&(a)[0]), 0))
#define dns_inline_assert(cond) ((void)(sizeof(struct { int : -!(cond); })))

#if HAVE___ASSUME
#define dns_assume(cond) __assume(cond)
#elif HAVE___BUILTIN_UNREACHABLE
#define dns_assume(cond)                                                                                               \
	do {                                                                                                               \
		if (!(cond)) __builtin_unreachable();                                                                          \
	} while (0)
#else
#define dns_assume(cond)                                                                                               \
	do {                                                                                                               \
		(void)(cond);                                                                                                  \
	} while (0)
#endif

#ifndef lengthof
#define lengthof(a) (dns_inline_assert(dns_isarray(a)), (sizeof(a) / sizeof(a)[0]))
#endif

#ifndef endof
#define endof(a) (dns_inline_assert(dns_isarray(a)), &(a)[lengthof((a))])
#endif

/*
 * M I S C E L L A N E O U S  C O M P A T
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#if _WIN32 || _WIN64
#define PRIuZ "Iu"
#else
#define PRIuZ "zu"
#endif

#ifndef DNS_THREAD_SAFE
#if (defined _REENTRANT || defined _THREAD_SAFE) && _POSIX_THREADS > 0
#define DNS_THREAD_SAFE 1
#else
#define DNS_THREAD_SAFE 0
#endif
#endif

#ifndef HAVE__STATIC_ASSERT
#define HAVE__STATIC_ASSERT                                                                                            \
	(dns_has_extension(c_static_assert) || DNS_GNUC_PREREQ(4, 6, 0) || __C11FEATURES__ || __STDC_VERSION__ >= 201112L)
#endif

#ifndef HAVE_STATIC_ASSERT
#if DNS_GNUC_PREREQ(0, 0, 0) && !DNS_GNUC_PREREQ(4, 6, 0)
#define HAVE_STATIC_ASSERT 0 /* glibc doesn't check GCC version */
#else
#if (defined static_assert)
#define HAVE_STATIC_ASSERT 1
#endif
#endif
#endif

#if HAVE_STATIC_ASSERT
#define dns_static_assert(cond, msg) static_assert(cond, msg)
#elif HAVE__STATIC_ASSERT
#define dns_static_assert(cond, msg) _Static_assert(cond, msg)
#else
#define dns_static_assert(cond, msg) extern char DNS_PP_XPASTE(dns_assert_, __LINE__)[sizeof(int[1 - 2 * !(cond)])]
#endif

/*
 * D E B U G  M A C R O S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

int *dns_debug_p(void) {
	static int debug;

	return &debug;
} /* dns_debug_p() */

#if DNS_DEBUG

#define DNS_SAY_(fmt, ...)                                                                                             \
	do {                                                                                                               \
		if (DNS_DEBUG > 0) fprintf(stderr, fmt "%.1s", __func__, __LINE__, __VA_ARGS__);                               \
	} while (0)
#define DNS_SAY(...) DNS_SAY_("@@ (%s:%d) " __VA_ARGS__, "\n")
#define DNS_HAI DNS_SAY("HAI")

#define DNS_SHOW_(P, fmt, ...)                                                                                         \
	do {                                                                                                               \
		if (DNS_DEBUG >= 1) {                                                                                          \
			fprintf(stderr, "@@ BEGIN * * * * * * * * * * * *\n");                                                     \
			fprintf(stderr, "@@ " fmt "%.0s\n", __VA_ARGS__);                                                          \
			dns_p_dump((P), stderr);                                                                                   \
			fprintf(stderr, "@@ END * * * * * * * * * * * * *\n\n");                                                   \
		}                                                                                                              \
	} while (0)

#define DNS_SHOW(...) DNS_SHOW_(__VA_ARGS__, "")

#else /* !DNS_DEBUG */

#undef DNS_DEBUG
#define DNS_DEBUG 0

#define DNS_SAY(...)
#define DNS_HAI
#define DNS_SHOW(...)

#endif /* DNS_DEBUG */

#define DNS_CARP(...) DNS_SAY(__VA_ARGS__)

/*
 * V E R S I O N  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

const char *dns_vendor(void) {
	return DNS_VENDOR;
} /* dns_vendor() */

int dns_v_rel(void) {
	return DNS_V_REL;
} /* dns_v_rel() */

int dns_v_abi(void) {
	return DNS_V_ABI;
} /* dns_v_abi() */

int dns_v_api(void) {
	return DNS_V_API;
} /* dns_v_api() */

/*
 * E R R O R  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#if _WIN32

#define DNS_EINTR WSAEINTR
#define DNS_EINPROGRESS WSAEINPROGRESS
#define DNS_EISCONN WSAEISCONN
#define DNS_EWOULDBLOCK WSAEWOULDBLOCK
#define DNS_EALREADY WSAEALREADY
#define DNS_EAGAIN EAGAIN
#define DNS_ETIMEDOUT WSAETIMEDOUT
#define DNS_ECONNREFUSED WSAECONNREFUSED
#define DNS_ECONNRESET WSAECONNRESET
#define DNS_ENETUNREACH WSAENETUNREACH
#define DNS_EHOSTUNREACH WSAEHOSTUNREACH

#define dns_syerr() ((int)GetLastError())
#define dns_soerr() ((int)WSAGetLastError())

#else

#define DNS_EINTR EINTR
#define DNS_EINPROGRESS EINPROGRESS
#define DNS_EISCONN EISCONN
#define DNS_EWOULDBLOCK EWOULDBLOCK
#define DNS_EALREADY EALREADY
#define DNS_EAGAIN EAGAIN
#define DNS_ETIMEDOUT ETIMEDOUT
#define DNS_ECONNREFUSED ECONNREFUSED
#define DNS_ECONNRESET ECONNRESET
#define DNS_ENETUNREACH ENETUNREACH
#define DNS_EHOSTUNREACH EHOSTUNREACH

#define dns_syerr() errno
#define dns_soerr() errno

#endif

const char *dns_strerror(int error) {
	switch (error) {
		case DNS_ENOBUFS:
			return "DNS packet buffer too small";
		case DNS_EILLEGAL:
			return "Illegal DNS RR name or data";
		case DNS_EORDER:
			return "Attempt to push RR out of section order";
		case DNS_ESECTION:
			return "Invalid section specified";
		case DNS_EUNKNOWN:
			return "Unknown DNS error";
		case DNS_EADDRESS:
			return "Invalid textual address form";
		case DNS_ENOQUERY:
			return "Bad execution state (missing query packet)";
		case DNS_ENOANSWER:
			return "Bad execution state (missing answer packet)";
		case DNS_EFETCHED:
			return "Answer already fetched";
		case DNS_ESERVICE:
			return "The service passed was not recognized for the specified socket type";
		case DNS_ENONAME:
			return "The name does not resolve for the supplied parameters";
		case DNS_EFAIL:
			return "A non-recoverable error occurred when attempting to resolve the name";
		default:
			return strerror(error);
	} /* switch() */
} /* dns_strerror() */

/*
 * A T O M I C  R O U T I N E S
 *
 * Use GCC's __atomic built-ins if possible. Unlike the __sync built-ins, we
 * can use the preprocessor to detect API and, more importantly, ISA
 * support. We want to avoid linking headaches where the API depends on an
 * external library if the ISA (e.g. i386) doesn't support lockless
 * operation.
 *
 * TODO: Support C11's atomic API. Although that may require some finesse
 * with how we define some public types, such as dns_atomic_t and struct
 * dns_resolv_conf.
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#ifndef HAVE___ATOMIC_FETCH_ADD
#if (defined __ATOMIC_RELAXED)
#define HAVE___ATOMIC_FETCH_ADD 1
#endif
#endif

#ifndef HAVE___ATOMIC_FETCH_SUB
#if (defined __ATOMIC_RELAXED)
#define HAVE___ATOMIC_FETCH_SUB 1
#endif
#endif

#ifndef DNS_ATOMIC_FETCH_ADD
#if HAVE___ATOMIC_FETCH_ADD && __GCC_ATOMIC_LONG_LOCK_FREE == 2
#define DNS_ATOMIC_FETCH_ADD(i) __atomic_fetch_add((i), 1, __ATOMIC_RELAXED)
#else
#pragma message("no atomic_fetch_add available")
#define DNS_ATOMIC_FETCH_ADD(i) ((*(i))++)
#endif
#endif

#ifndef DNS_ATOMIC_FETCH_SUB
#if HAVE___ATOMIC_FETCH_SUB && __GCC_ATOMIC_LONG_LOCK_FREE == 2
#define DNS_ATOMIC_FETCH_SUB(i) __atomic_fetch_sub((i), 1, __ATOMIC_RELAXED)
#else
#pragma message("no atomic_fetch_sub available")
#define DNS_ATOMIC_FETCH_SUB(i) ((*(i))--)
#endif
#endif

static DNS_INLINE unsigned dns_atomic_fetch_add(dns_atomic_t *i) {
	return DNS_ATOMIC_FETCH_ADD(i);
} /* dns_atomic_fetch_add() */

static DNS_INLINE unsigned dns_atomic_fetch_sub(dns_atomic_t *i) {
	return DNS_ATOMIC_FETCH_SUB(i);
} /* dns_atomic_fetch_sub() */

/*
 * C R Y P T O  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/*
 * P R N G
 */

#ifndef DNS_RANDOM
#if defined(HAVE_ARC4RANDOM) || defined(__OpenBSD__) || defined(__FreeBSD__) || defined(__NetBSD__) ||                 \
    defined(__APPLE__)
#define DNS_RANDOM arc4random
#elif __linux__
#define DNS_RANDOM random
#else
#define DNS_RANDOM rand
#endif
#endif

#define DNS_RANDOM_arc4random 1
#define DNS_RANDOM_random 2
#define DNS_RANDOM_rand 3
#define DNS_RANDOM_RAND_bytes 4

#define DNS_RANDOM_OPENSSL (DNS_RANDOM_RAND_bytes == DNS_PP_XPASTE(DNS_RANDOM_, DNS_RANDOM))

#if DNS_RANDOM_OPENSSL
#include <openssl/rand.h>
#endif

static unsigned dns_random_(void) {
#if DNS_RANDOM_OPENSSL
	unsigned r;
	_Bool ok;

	ok = (1 == RAND_bytes((unsigned char *)&r, sizeof r));
	assert(ok && "1 == RAND_bytes()");

	return r;
#else
	return DNS_RANDOM();
#endif
} /* dns_random_() */

dns_random_f **dns_random_p(void) {
	static dns_random_f *random_f = &dns_random_;

	return &random_f;
} /* dns_random_p() */

/*
 * P E R M U T A T I O N  G E N E R A T O R
 */

#define DNS_K_TEA_KEY_SIZE 16
#define DNS_K_TEA_BLOCK_SIZE 8
#define DNS_K_TEA_CYCLES 32
#define DNS_K_TEA_MAGIC 0x9E3779B9U

struct dns_k_tea {
	uint32_t key[DNS_K_TEA_KEY_SIZE / sizeof(uint32_t)];
	unsigned cycles;
}; /* struct dns_k_tea */

static void dns_k_tea_init(struct dns_k_tea *tea, uint32_t key[], unsigned cycles) {
	memcpy(tea->key, key, sizeof tea->key);

	tea->cycles = (cycles) ? cycles : DNS_K_TEA_CYCLES;
} /* dns_k_tea_init() */

static void dns_k_tea_encrypt(struct dns_k_tea *tea, uint32_t v[], uint32_t *w) {
	uint32_t y, z, sum, n;

	y = v[0];
	z = v[1];
	sum = 0;

	for (n = 0; n < tea->cycles; n++) {
		sum += DNS_K_TEA_MAGIC;
		y += ((z << 4) + tea->key[0]) ^ (z + sum) ^ ((z >> 5) + tea->key[1]);
		z += ((y << 4) + tea->key[2]) ^ (y + sum) ^ ((y >> 5) + tea->key[3]);
	}

	w[0] = y;
	w[1] = z;

	return /* void */;
} /* dns_k_tea_encrypt() */

/*
 * Permutation generator, based on a Luby-Rackoff Feistel construction.
 *
 * Specifically, this is a generic balanced Feistel block cipher using TEA
 * (another block cipher) as the pseudo-random function, F. At best it's as
 * strong as F (TEA), notwithstanding the seeding. F could be AES, SHA-1, or
 * perhaps Bernstein's Salsa20 core; I am naively trying to keep things
 * simple.
 *
 * The generator can create a permutation of any set of numbers, as long as
 * the size of the set is an even power of 2. This limitation arises either
 * out of an inherent property of balanced Feistel constructions, or by my
 * own ignorance. I'll tackle an unbalanced construction after I wrap my
 * head around Schneier and Kelsey's paper.
 *
 * CAVEAT EMPTOR. IANAC.
 */
#define DNS_K_PERMUTOR_ROUNDS 8

struct dns_k_permutor {
	unsigned stepi, length, limit;
	unsigned shift, mask, rounds;

	struct dns_k_tea tea;
}; /* struct dns_k_permutor */

static DNS_INLINE unsigned dns_k_permutor_powof(unsigned n) {
	unsigned m, i = 0;

	for (m = 1; m < n; m <<= 1, i++)
		;
	;

	return i;
} /* dns_k_permutor_powof() */

static void dns_k_permutor_init(struct dns_k_permutor *p, unsigned low, unsigned high) {
	uint32_t key[DNS_K_TEA_KEY_SIZE / sizeof(uint32_t)];
	unsigned width, i;

	p->stepi = 0;

	p->length = (high - low) + 1;
	p->limit = high;

	width = dns_k_permutor_powof(p->length);
	width += width % 2;

	p->shift = width / 2;
	p->mask = (1U << p->shift) - 1;
	p->rounds = DNS_K_PERMUTOR_ROUNDS;

	for (i = 0; i < lengthof(key); i++)
		key[i] = dns_random();

	dns_k_tea_init(&p->tea, key, 0);

	return /* void */;
} /* dns_k_permutor_init() */

static unsigned dns_k_permutor_F(struct dns_k_permutor *p, unsigned k, unsigned x) {
	uint32_t in[DNS_K_TEA_BLOCK_SIZE / sizeof(uint32_t)], out[DNS_K_TEA_BLOCK_SIZE / sizeof(uint32_t)];

	memset(in, '\0', sizeof in);

	in[0] = k;
	in[1] = x;

	dns_k_tea_encrypt(&p->tea, in, out);

	return p->mask & out[0];
} /* dns_k_permutor_F() */

static unsigned dns_k_permutor_E(struct dns_k_permutor *p, unsigned n) {
	unsigned l[2], r[2];
	unsigned i;

	i = 0;
	l[i] = p->mask & (n >> p->shift);
	r[i] = p->mask & (n >> 0);

	do {
		l[(i + 1) % 2] = r[i % 2];
		r[(i + 1) % 2] = l[i % 2] ^ dns_k_permutor_F(p, i, r[i % 2]);

		i++;
	} while (i < p->rounds - 1);

	return ((l[i % 2] & p->mask) << p->shift) | ((r[i % 2] & p->mask) << 0);
} /* dns_k_permutor_E() */

DNS_NOTUSED static unsigned dns_k_permutor_D(struct dns_k_permutor *p, unsigned n) {
	unsigned l[2], r[2];
	unsigned i;

	i = p->rounds - 1;
	l[i % 2] = p->mask & (n >> p->shift);
	r[i % 2] = p->mask & (n >> 0);

	do {
		i--;

		r[i % 2] = l[(i + 1) % 2];
		l[i % 2] = r[(i + 1) % 2] ^ dns_k_permutor_F(p, i, l[(i + 1) % 2]);
	} while (i > 0);

	return ((l[i % 2] & p->mask) << p->shift) | ((r[i % 2] & p->mask) << 0);
} /* dns_k_permutor_D() */

static unsigned dns_k_permutor_step(struct dns_k_permutor *p) {
	unsigned n;

	do {
		n = dns_k_permutor_E(p, p->stepi++);
	} while (n >= p->length);

	return n + (p->limit + 1 - p->length);
} /* dns_k_permutor_step() */

/*
 * Simple permutation box. Useful for shuffling rrsets from an iterator.
 * Uses AES s-box to provide good diffusion.
 *
 * Seems to pass muster under runs test.
 *
 * $ for i in 0 1 2 3 4 5 6 7 8 9; do ./dns shuffle-16 > /tmp/out; done
 * $ R -q -f /dev/stdin 2>/dev/null <<-EOF | awk '/p-value/{ print $8 }'
 * 	library(lawstat)
 * 	runs.test(scan(file="/tmp/out"))
 * EOF
 */
static unsigned short dns_k_shuffle16(unsigned short n, unsigned s) {
	static const unsigned char sbox[256] = {
	    0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76, 0xca, 0x82,
	    0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, 0xb7, 0xfd, 0x93, 0x26,
	    0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15, 0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96,
	    0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0,
	    0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb,
	    0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, 0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f,
	    0x50, 0x3c, 0x9f, 0xa8, 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff,
	    0xf3, 0xd2, 0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
	    0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb, 0xe0, 0x32,
	    0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, 0xe7, 0xc8, 0x37, 0x6d,
	    0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08, 0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6,
	    0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a, 0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e,
	    0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, 0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e,
	    0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, 0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f,
	    0xb0, 0x54, 0xbb, 0x16};
	unsigned char a, b;
	unsigned i;

	a = 0xff & (n >> 0);
	b = 0xff & (n >> 8);

	for (i = 0; i < 4; i++) {
		a ^= 0xff & s;
		a = sbox[a] ^ b;
		b = sbox[b] ^ a;
		s >>= 8;
	}

	return ((0xff00 & (a << 8)) | (0x00ff & (b << 0)));
} /* dns_k_shuffle16() */

/*
 * U T I L I T Y  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#define DNS_MAXINTERVAL 300

struct dns_clock {
	time_t sample, elapsed;
}; /* struct dns_clock */

static void dns_begin(struct dns_clock *clk) {
	clk->sample = time(0);
	clk->elapsed = 0;
} /* dns_begin() */

static time_t dns_elapsed(struct dns_clock *clk) {
	time_t curtime;

	if ((time_t)-1 == time(&curtime)) return clk->elapsed;

	if (curtime > clk->sample) clk->elapsed += (time_t)DNS_PP_MIN(difftime(curtime, clk->sample), DNS_MAXINTERVAL);

	clk->sample = curtime;

	return clk->elapsed;
} /* dns_elapsed() */

DNS_NOTUSED static size_t dns_strnlen(const char *src, size_t m) {
	size_t n = 0;

	while (*src++ && n < m)
		++n;

	return n;
} /* dns_strnlen() */

DNS_NOTUSED static size_t dns_strnlcpy(char *dst, size_t lim, const char *src, size_t max) {
	size_t len = dns_strnlen(src, max), n;

	if (lim > 0) {
		n = DNS_PP_MIN(lim - 1, len);
		memcpy(dst, src, n);
		dst[n] = '\0';
	}

	return len;
} /* dns_strnlcpy() */

#if (defined AF_UNIX && !defined _WIN32)
#define DNS_HAVE_SOCKADDR_UN 1
#endif

static size_t dns_af_len(int af) {
	static const size_t table[AF_MAX] = {
		[AF_INET6] = sizeof(struct sockaddr_in6),
		[AF_INET] = sizeof(struct sockaddr_in),
#if DNS_HAVE_SOCKADDR_UN
		[AF_UNIX] = sizeof(struct sockaddr_un),
#endif
	};

	return table[af];
} /* dns_af_len() */

#define dns_sa_family(sa) (((struct sockaddr_storage *)(sa))->ss_family)

#define dns_sa_len(sa) dns_af_len(dns_sa_family(sa))

#define DNS_SA_NOPORT &dns_sa_noport
static unsigned short dns_sa_noport;

static unsigned short *dns_sa_port(int af, void *sa) {
	switch (af) {
		case AF_INET6:
			return &((struct sockaddr_in6 *)sa)->sin6_port;
		case AF_INET:
			return &((struct sockaddr_in *)sa)->sin_port;
		default:
			return DNS_SA_NOPORT;
	}
} /* dns_sa_port() */

static void *dns_sa_addr(int af, const void *sa, socklen_t *size) {
	switch (af) {
		case AF_INET6: {
			struct in6_addr *in6 = &((struct sockaddr_in6 *)sa)->sin6_addr;

			if (size) *size = sizeof *in6;

			return in6;
		}
		case AF_INET: {
			struct in_addr *in = &((struct sockaddr_in *)sa)->sin_addr;

			if (size) *size = sizeof *in;

			return in;
		}
		default:
			if (size) *size = 0;

			return 0;
	}
} /* dns_sa_addr() */

#if DNS_HAVE_SOCKADDR_UN
#define DNS_SUNPATHMAX (sizeof((struct sockaddr_un *)0)->sun_path)
#endif

DNS_NOTUSED static void *dns_sa_path(void *sa, socklen_t *size) {
	switch (dns_sa_family(sa)) {
#if DNS_HAVE_SOCKADDR_UN
		case AF_UNIX: {
			char *path = ((struct sockaddr_un *)sa)->sun_path;

			if (size) *size = dns_strnlen(path, DNS_SUNPATHMAX);

			return path;
		}
#endif
		default:
			if (size) *size = 0;

			return NULL;
	}
} /* dns_sa_path() */

static int dns_sa_cmp(void *a, void *b) {
	int cmp, af;

	if ((cmp = dns_sa_family(a) - dns_sa_family(b))) return cmp;

	switch ((af = dns_sa_family(a))) {
		case AF_INET: {
			struct in_addr *a4, *b4;

			if ((cmp = htons(*dns_sa_port(af, a)) - htons(*dns_sa_port(af, b)))) return cmp;

			a4 = dns_sa_addr(af, a, NULL);
			b4 = dns_sa_addr(af, b, NULL);

			if (ntohl(a4->s_addr) < ntohl(b4->s_addr)) return -1;
			if (ntohl(a4->s_addr) > ntohl(b4->s_addr)) return 1;

			return 0;
		}
		case AF_INET6: {
			struct in6_addr *a6, *b6;
			size_t i;

			if ((cmp = htons(*dns_sa_port(af, a)) - htons(*dns_sa_port(af, b)))) return cmp;

			a6 = dns_sa_addr(af, a, NULL);
			b6 = dns_sa_addr(af, b, NULL);

			/* XXX: do we need to use in6_clearscope()? */
			for (i = 0; i < sizeof a6->s6_addr; i++) {
				if ((cmp = a6->s6_addr[i] - b6->s6_addr[i])) return cmp;
			}

			return 0;
		}
#if DNS_HAVE_SOCKADDR_UN
		case AF_UNIX: {
			char a_path[DNS_SUNPATHMAX + 1], b_path[sizeof a_path];

			dns_strnlcpy(a_path, sizeof a_path, dns_sa_path(a, NULL), DNS_SUNPATHMAX);
			dns_strnlcpy(b_path, sizeof b_path, dns_sa_path(b, NULL), DNS_SUNPATHMAX);

			return strcmp(a_path, b_path);
		}
#endif
		default:
			return -1;
	}
} /* dns_sa_cmp() */

#if _WIN32
static int dns_inet_pton(int af, const void *src, void *dst) {
	union {
		struct sockaddr_in sin;
		struct sockaddr_in6 sin6;
	} u;

	u.sin.sin_family = af;

	if (0 != WSAStringToAddressA((void *)src, af, (void *)0, (struct sockaddr *)&u, &(int){sizeof u})) return -1;

	switch (af) {
		case AF_INET6:
			*(struct in6_addr *)dst = u.sin6.sin6_addr;

			return 1;
		case AF_INET:
			*(struct in_addr *)dst = u.sin.sin_addr;

			return 1;
		default:
			return 0;
	}
} /* dns_inet_pton() */

static const char *dns_inet_ntop(int af, const void *src, void *dst, unsigned long lim) {
	union {
		struct sockaddr_in sin;
		struct sockaddr_in6 sin6;
	} u;

	/* NOTE: WSAAddressToString will print .sin_port unless zeroed. */
	memset(&u, 0, sizeof u);

	u.sin.sin_family = af;

	switch (af) {
		case AF_INET6:
			u.sin6.sin6_addr = *(struct in6_addr *)src;
			break;
		case AF_INET:
			u.sin.sin_addr = *(struct in_addr *)src;

			break;
		default:
			return 0;
	}

	if (0 != WSAAddressToStringA((struct sockaddr *)&u, dns_sa_len(&u), (void *)0, dst, &lim)) return 0;

	return dst;
} /* dns_inet_ntop() */
#else
#define dns_inet_pton(...) inet_pton(__VA_ARGS__)
#define dns_inet_ntop(...) inet_ntop(__VA_ARGS__)
#endif

static dns_error_t dns_pton(int af, const void *src, void *dst) {
	switch (dns_inet_pton(af, src, dst)) {
		case 1:
			return 0;
		case -1:
			return dns_soerr();
		default:
			return DNS_EADDRESS;
	}
} /* dns_pton() */

static dns_error_t dns_ntop(int af, const void *src, void *dst, unsigned long lim) {
	return (dns_inet_ntop(af, src, dst, lim)) ? 0 : dns_soerr();
} /* dns_ntop() */

size_t dns_strlcpy(char *dst, const char *src, size_t lim) {
	char *d = dst;
	char *e = &dst[lim];
	const char *s = src;

	if (d < e) {
		do {
			if ('\0' == (*d++ = *s++)) return s - src - 1;
		} while (d < e);

		d[-1] = '\0';
	}

	while (*s++ != '\0')
		;
	;

	return s - src - 1;
} /* dns_strlcpy() */

size_t dns_strlcat(char *dst, const char *src, size_t lim) {
	char *d = memchr(dst, '\0', lim);
	char *e = &dst[lim];
	const char *s = src;
	const char *p;

	if (d && d < e) {
		do {
			if ('\0' == (*d++ = *s++)) return d - dst - 1;
		} while (d < e);

		d[-1] = '\0';
	}

	p = s;

	while (*s++ != '\0')
		;
	;

	return lim + (s - p - 1);
} /* dns_strlcat() */

#if _WIN32

static char *dns_strsep(char **sp, const char *delim) {
	char *p;

	if (!(p = *sp)) return 0;

	*sp += strcspn(p, delim);

	if (**sp != '\0') {
		**sp = '\0';
		++*sp;
	} else *sp = NULL;

	return p;
} /* dns_strsep() */

#else
#define dns_strsep(...) strsep(__VA_ARGS__)
#endif

#if _WIN32
#ifndef strcasecmp
#define strcasecmp(...) _stricmp(__VA_ARGS__)
#endif
#ifndef strncasecmp
#define strncasecmp(...) _strnicmp(__VA_ARGS__)
#endif
#endif

static DNS_INLINE _Bool dns_isalpha(unsigned char c) {
	return isalpha(c);
} /* dns_isalpha() */

static DNS_INLINE _Bool dns_isdigit(unsigned char c) {
	return isdigit(c);
} /* dns_isdigit() */

static DNS_INLINE _Bool dns_isalnum(unsigned char c) {
	return isalnum(c);
} /* dns_isalnum() */

static DNS_INLINE _Bool dns_isspace(unsigned char c) {
	return isspace(c);
} /* dns_isspace() */

static int dns_poll(int fd, short events, int timeout) {
/* For our usage in belle sip, we are called by the main loop when something is to read on the dns socket.
 * As a result there is no need to perform a blocking select.
 **/
#if 0
	fd_set rset, wset;

	if (!events)
		return 0;

	assert(fd >= 0 && (unsigned)fd < FD_SETSIZE);

	FD_ZERO(&rset);
	FD_ZERO(&wset);

	if (events & DNS_POLLIN)
		FD_SET(fd, &rset);

	if (events & DNS_POLLOUT)
		FD_SET(fd, &wset);

	select(fd + 1, &rset, &wset, 0, (timeout >= 0)? &(struct timeval){ timeout, 0 } : NULL);

#endif
	return 0;
} /* dns_poll() */

#if !_WIN32
DNS_NOTUSED static int dns_sigmask(int how, const sigset_t *set, sigset_t *oset) {
#if DNS_THREAD_SAFE
	return pthread_sigmask(how, set, oset);
#else
	return (0 == sigprocmask(how, set, oset)) ? 0 : errno;
#endif
} /* dns_sigmask() */
#endif

static long dns_send(int fd, const void *src, size_t lim, int flags) {
#if _WIN32 || !defined SIGPIPE || defined SO_NOSIGPIPE
	return send(fd, src, lim, flags);
#elif defined MSG_NOSIGNAL
	return send(fd, src, lim, flags | MSG_NOSIGNAL);
#elif _POSIX_REALTIME_SIGNALS > 0 /* require sigtimedwait */
	/*
	 * SIGPIPE handling similar to the approach described in
	 * http://krokisplace.blogspot.com/2010/02/suppressing-sigpipe-in-library.html
	 */
	sigset_t pending, blocked, piped;
	long count;
	int saved, error;

	sigemptyset(&pending);
	sigpending(&pending);

	if (!sigismember(&pending, SIGPIPE)) {
		sigemptyset(&piped);
		sigaddset(&piped, SIGPIPE);
		sigemptyset(&blocked);

		if ((error = dns_sigmask(SIG_BLOCK, &piped, &blocked))) goto error;
	}

	count = send(fd, src, lim, flags);

	if (!sigismember(&pending, SIGPIPE)) {
		saved = errno;

		if (count == -1 && errno == EPIPE) {
			while (-1 == sigtimedwait(&piped, NULL, &(struct timespec){0, 0}) && errno == EINTR)
				;
			;
		}

		if ((error = dns_sigmask(SIG_SETMASK, &blocked, NULL))) goto error;

		errno = saved;
	}

	return count;
error:
	errno = error;

	return -1;
#else
#error "unable to suppress SIGPIPE"
	return send(fd, src, lim, flags);
#endif
} /* dns_send() */

#define DNS_FOPEN_STDFLAGS "rwabt+"

static dns_error_t dns_fopen_addflag(char *dst, const char *src, size_t lim, int fc) {
	char *p = dst, *pe = dst + lim;

	/* copy standard flags */
	while (*src && strchr(DNS_FOPEN_STDFLAGS, *src)) {
		if (!(p < pe)) return ENOMEM;
		*p++ = *src++;
	}

	/* append flag to standard flags */
	if (!(p < pe)) return ENOMEM;
	*p++ = fc;

	/* copy remaining mode string, including '\0' */
	do {
		if (!(p < pe)) return ENOMEM;
	} while ((*p++ = *src++));

	return 0;
} /* dns_fopen_addflag() */

static FILE *dns_fopen(const char *path, const char *mode, dns_error_t *_error) {
	FILE *fp;
	char mode_cloexec[32];
	int error;

	assert(path && mode && *mode);
	if (!*path) {
		error = EINVAL;
		goto error;
	}

#if _WIN32 || _WIN64
	if ((error = dns_fopen_addflag(mode_cloexec, mode, sizeof mode_cloexec, 'N'))) goto error;
	if (!(fp = fopen(path, mode_cloexec))) goto syerr;
#else
	if ((error = dns_fopen_addflag(mode_cloexec, mode, sizeof mode_cloexec, 'e'))) goto error;
	if (!(fp = fopen(path, mode_cloexec))) {
		if (errno != EINVAL) goto syerr;
		if (!(fp = fopen(path, mode))) goto syerr;
	}
#endif

	return fp;
syerr:
	error = dns_syerr();
error:
	*_error = error;

	return NULL;
} /* dns_fopen() */

/*
 * F I X E D - S I Z E D  B U F F E R  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#define DNS_B_INIT(src, n)                                                                                             \
	{ (unsigned char *)(src), (unsigned char *)(src), (unsigned char *)(src) + (n), }

#define DNS_B_FROM(src, n) DNS_B_INIT((src), (n))
#define DNS_B_INTO(src, n) DNS_B_INIT((src), (n))

struct dns_buf {
	const unsigned char *base;
	unsigned char *p;
	const unsigned char *pe;
	dns_error_t error;
	size_t overflow;
}; /* struct dns_buf */

static DNS_INLINE size_t dns_b_tell(struct dns_buf *b) {
	return b->p - b->base;
}

static DNS_INLINE dns_error_t dns_b_setoverflow(struct dns_buf *b, size_t n, dns_error_t error) {
	b->overflow += n;
	return b->error = error;
}

DNS_NOTUSED static struct dns_buf *dns_b_into(struct dns_buf *b, void *src, size_t n) {
	*b = (struct dns_buf)DNS_B_INTO(src, n);

	return b;
}

static dns_error_t dns_b_putc(struct dns_buf *b, unsigned char uc) {
	if (!(b->p < b->pe)) return dns_b_setoverflow(b, 1, DNS_ENOBUFS);

	*b->p++ = uc;

	return 0;
}

static dns_error_t dns_b_pputc(struct dns_buf *b, unsigned char uc, size_t p) {
	size_t pe = b->pe - b->base;
	if (pe <= p) return dns_b_setoverflow(b, p - pe + 1, DNS_ENOBUFS);

	*((unsigned char *)b->base + p) = uc;

	return 0;
}

static DNS_INLINE dns_error_t dns_b_put16(struct dns_buf *b, uint16_t u) {
	return dns_b_putc(b, u >> 8), dns_b_putc(b, u >> 0);
}

static DNS_INLINE dns_error_t dns_b_pput16(struct dns_buf *b, uint16_t u, size_t p) {
	if (dns_b_pputc(b, u >> 8, p) || dns_b_pputc(b, u >> 0, p + 1)) return b->error;

	return 0;
}

DNS_NOTUSED static DNS_INLINE dns_error_t dns_b_put32(struct dns_buf *b, uint32_t u) {
	return dns_b_putc(b, u >> 24), dns_b_putc(b, u >> 16), dns_b_putc(b, u >> 8), dns_b_putc(b, u >> 0);
}

static dns_error_t dns_b_put(struct dns_buf *b, const void *src, size_t len) {
	size_t n = DNS_PP_MIN((size_t)(b->pe - b->p), len);

	memcpy(b->p, src, n);
	b->p += n;

	if (n < len) return dns_b_setoverflow(b, len - n, DNS_ENOBUFS);

	return 0;
}

static dns_error_t dns_b_puts(struct dns_buf *b, const void *src) {
	return dns_b_put(b, src, strlen(src));
}

DNS_NOTUSED static DNS_INLINE dns_error_t dns_b_fmtju(struct dns_buf *b, const uintmax_t u, const unsigned width) {
	size_t digits, padding, overflow;
	uintmax_t r;
	unsigned char *tp, *te, tc;

	digits = 0;
	r = u;
	do {
		digits++;
		r /= 10;
	} while (r);

	padding = width - DNS_PP_MIN(digits, width);
	overflow = (digits + padding) - DNS_PP_MIN((size_t)(b->pe - b->p), (digits + padding));

	while (padding--) {
		dns_b_putc(b, '0');
	}

	digits = 0;
	tp = b->p;
	r = u;
	do {
		if (overflow < ++digits) dns_b_putc(b, '0' + (r % 10));
		r /= 10;
	} while (r);

	te = b->p;
	while (tp < te) {
		tc = *--te;
		*te = *tp;
		*tp++ = tc;
	}

	return b->error;
}

static void dns_b_popc(struct dns_buf *b) {
	if (b->overflow && !--b->overflow) b->error = 0;
	if (b->p > b->base) b->p--;
}

static DNS_INLINE const char *dns_b_tolstring(struct dns_buf *b, size_t *n) {
	if (b->p < b->pe) {
		*b->p = '\0';
		*n = b->p - b->base;

		return (const char *)b->base;
	} else if (b->p > b->base) {
		if (b->p[-1] != '\0') {
			dns_b_setoverflow(b, 1, DNS_ENOBUFS);
			b->p[-1] = '\0';
		}
		*n = &b->p[-1] - b->base;

		return (const char *)b->base;
	} else {
		*n = 0;

		return "";
	}
}

static DNS_INLINE const char *dns_b_tostring(struct dns_buf *b) {
	size_t n;
	return dns_b_tolstring(b, &n);
}

static DNS_INLINE size_t dns_b_strlen(struct dns_buf *b) {
	size_t n;
	dns_b_tolstring(b, &n);
	return n;
}

static DNS_INLINE size_t dns_b_strllen(struct dns_buf *b) {
	size_t n = dns_b_strlen(b);
	return n + b->overflow;
}

DNS_NOTUSED static const struct dns_buf *dns_b_from(const struct dns_buf *b, const void *src, size_t n) {
	*(struct dns_buf *)b = (struct dns_buf)DNS_B_FROM(src, n);

	return b;
}

static DNS_INLINE int dns_b_getc(const struct dns_buf *_b, const int eof) {
	struct dns_buf *b = (struct dns_buf *)_b;

	if (!(b->p < b->pe)) return dns_b_setoverflow(b, 1, DNS_EILLEGAL), eof;

	return *b->p++;
}

static DNS_INLINE intmax_t dns_b_get16(const struct dns_buf *b, const intmax_t eof) {
	intmax_t n;

	n = (dns_b_getc(b, 0) << 8);
	n |= (dns_b_getc(b, 0) << 0);

	return (!b->overflow) ? n : eof;
}

DNS_NOTUSED static DNS_INLINE intmax_t dns_b_get32(const struct dns_buf *b, const intmax_t eof) {
	intmax_t n;

	n = (dns_b_get16(b, 0) << 16);
	n |= (dns_b_get16(b, 0) << 0);

	return (!b->overflow) ? n : eof;
}

static DNS_INLINE dns_error_t dns_b_move(struct dns_buf *dst, const struct dns_buf *_src, size_t n) {
	struct dns_buf *src = (struct dns_buf *)_src;
	size_t src_n = DNS_PP_MIN((size_t)(src->pe - src->p), n);
	size_t src_r = n - src_n;

	dns_b_put(dst, src->p, src_n);
	src->p += src_n;

	if (src_r) return dns_b_setoverflow(src, src_r, DNS_EILLEGAL);

	return dst->error;
}

/*
 * P A C K E T  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

unsigned dns_p_count(struct dns_packet *P, enum dns_section section) {
	unsigned count;

	switch (section) {
		case DNS_S_QD:
			return ntohs(dns_header(P)->qdcount);
		case DNS_S_AN:
			return ntohs(dns_header(P)->ancount);
		case DNS_S_NS:
			return ntohs(dns_header(P)->nscount);
		case DNS_S_AR:
			return ntohs(dns_header(P)->arcount);
		default:
			count = 0;

			if (section & DNS_S_QD) count += ntohs(dns_header(P)->qdcount);
			if (section & DNS_S_AN) count += ntohs(dns_header(P)->ancount);
			if (section & DNS_S_NS) count += ntohs(dns_header(P)->nscount);
			if (section & DNS_S_AR) count += ntohs(dns_header(P)->arcount);

			return count;
	}
} /* dns_p_count() */

struct dns_packet *dns_p_init(struct dns_packet *P, size_t size) {
	if (!P) return 0;

	assert(size >= offsetof(struct dns_packet, data) + 12);

	memset(P, 0, sizeof *P);
	P->size = size - offsetof(struct dns_packet, data);
	P->end = 12;

	memset(P->data, '\0', 12);

	return P;
} /* dns_p_init() */

static struct dns_packet *dns_p_reset(struct dns_packet *P) {
	return dns_p_init(P, offsetof(struct dns_packet, data) + P->size);
} /* dns_p_reset() */

static unsigned short dns_p_qend(struct dns_packet *P) {
	unsigned short qend = 12;
	unsigned i, count = dns_p_count(P, DNS_S_QD);

	for (i = 0; i < count && qend < P->end; i++) {
		if (P->end == (qend = dns_d_skip(qend, P))) goto invalid;

		if (P->end - qend < 4) goto invalid;

		qend += 4;
	}

	return DNS_PP_MIN(qend, P->end);
invalid:
	return P->end;
} /* dns_p_qend() */

struct dns_packet *dns_p_make(size_t len, int *error) {
	struct dns_packet *P;
	size_t size = dns_p_calcsize(len);

	if (!(P = dns_p_init(malloc(size), size))) *error = dns_syerr();

	return P;
} /* dns_p_make() */

static void dns_p_free(struct dns_packet *P) {
	free(P);
} /* dns_p_free() */

/* convience routine to free any existing packet before storing new packet */
static struct dns_packet *dns_p_setptr(struct dns_packet **dst, struct dns_packet *src) {
	dns_p_free(*dst);

	*dst = src;

	return src;
} /* dns_p_setptr() */

static struct dns_packet *dns_p_movptr(struct dns_packet **dst, struct dns_packet **src) {
	dns_p_setptr(dst, *src);

	*src = NULL;

	return *dst;
} /* dns_p_movptr() */

int dns_p_grow(struct dns_packet **P) {
	struct dns_packet *tmp;
	size_t size;
	int error;

	if (!*P) {
		if (!(*P = dns_p_make(DNS_P_QBUFSIZ, &error))) return error;

		return 0;
	}

	size = dns_p_sizeof(*P);
	size |= size >> 1;
	size |= size >> 2;
	size |= size >> 4;
	size |= size >> 8;
	size++;

	if (size > 65536) return DNS_ENOBUFS;

	if (!(tmp = realloc(*P, dns_p_calcsize(size)))) return dns_syerr();

	tmp->size = size;
	*P = tmp;

	return 0;
} /* dns_p_grow() */

struct dns_packet *dns_p_copy(struct dns_packet *P, const struct dns_packet *P0) {
	if (!P) return 0;

	P->end = DNS_PP_MIN(P->size, P0->end);

	memcpy(P->data, P0->data, P->end);

	return P;
} /* dns_p_copy() */

struct dns_packet *
dns_p_merge(struct dns_packet *A, enum dns_section Amask, struct dns_packet *B, enum dns_section Bmask, int *error_) {
	size_t bufsiz = DNS_PP_MIN(65535, ((A) ? A->end : 0) + ((B) ? B->end : 0));
	struct dns_packet *M;
	enum dns_section section;
	struct dns_rr rr, mr;
	int error, copy;

	if (!A && B) {
		A = B;
		Amask = Bmask;
		B = 0;
	}

merge:
	if (!(M = dns_p_make(bufsiz, &error))) goto error;

	for (section = DNS_S_QD; (DNS_S_ALL & section); section <<= 1) {
		if (A && (section & Amask)) {
			dns_rr_foreach(&rr, A, .section = section) {
				if ((error = dns_rr_copy(M, &rr, A))) goto error;
			}
		}

		if (B && (section & Bmask)) {
			dns_rr_foreach(&rr, B, .section = section) {
				copy = 1;

				dns_rr_foreach(&mr, M, .type = rr.type, .section = DNS_S_ALL) {
					if (!(copy = dns_rr_cmp(&rr, B, &mr, M))) break;
				}

				if (copy && (error = dns_rr_copy(M, &rr, B))) goto error;
			}
		}
	}

	return M;
error:
	dns_p_setptr(&M, NULL);

	if (error == DNS_ENOBUFS && bufsiz < 65535) {
		bufsiz = DNS_PP_MIN(65535, bufsiz * 2);

		goto merge;
	}

	*error_ = error;

	return 0;
} /* dns_p_merge() */

static unsigned short dns_l_skip(unsigned short, const unsigned char *, size_t);

void dns_p_dictadd(struct dns_packet *P, unsigned short dn) {
	unsigned short lp, lptr, i;

	lp = dn;

	while (lp < P->end) {
		if (0xc0 == (0xc0 & P->data[lp]) && P->end - lp >= 2 && lp != dn) {
			lptr = ((0x3f & P->data[lp + 0]) << 8) | ((0xff & P->data[lp + 1]) << 0);

			for (i = 0; i < lengthof(P->dict) && P->dict[i]; i++) {
				if (P->dict[i] == lptr) {
					P->dict[i] = dn;

					return;
				}
			}
		}

		lp = dns_l_skip(lp, P->data, P->end);
	}

	for (i = 0; i < lengthof(P->dict); i++) {
		if (!P->dict[i]) {
			P->dict[i] = dn;

			break;
		}
	}
} /* dns_p_dictadd() */

int dns_p_push(struct dns_packet *P,
               enum dns_section section,
               const void *dn,
               size_t dnlen,
               enum dns_type type,
               enum dns_class class,
               unsigned ttl,
               const void *any) {
	size_t end = P->end;
	int error;

	if ((error = dns_d_push(P, dn, dnlen))) goto error;

	if (P->size - P->end < 4) goto nobufs;

	P->data[P->end++] = 0xff & (type >> 8);
	P->data[P->end++] = 0xff & (type >> 0);

	P->data[P->end++] = 0xff & (class >> 8);
	P->data[P->end++] = 0xff & (class >> 0);

	if (section == DNS_S_QD) goto update;

	if (P->size - P->end < 6) goto nobufs;

	if (type != DNS_T_OPT) ttl = DNS_PP_MIN(ttl, 0x7fffffffU);
	P->data[P->end++] = ttl >> 24;
	P->data[P->end++] = ttl >> 16;
	P->data[P->end++] = ttl >> 8;
	P->data[P->end++] = ttl >> 0;

	if ((error = dns_any_push(P, (union dns_any *)any, type))) goto error;

update:
	switch (section) {
		case DNS_S_QD:
			if (dns_p_count(P, DNS_S_AN | DNS_S_NS | DNS_S_AR)) goto order;

			if (!P->memo.qd.base && (error = dns_p_study(P))) goto error;

			dns_header(P)->qdcount = htons(ntohs(dns_header(P)->qdcount) + 1);

			P->memo.qd.end = P->end;
			P->memo.an.base = P->end;
			P->memo.an.end = P->end;
			P->memo.ns.base = P->end;
			P->memo.ns.end = P->end;
			P->memo.ar.base = P->end;
			P->memo.ar.end = P->end;

			break;
		case DNS_S_AN:
			if (dns_p_count(P, DNS_S_NS | DNS_S_AR)) goto order;

			if (!P->memo.an.base && (error = dns_p_study(P))) goto error;

			dns_header(P)->ancount = htons(ntohs(dns_header(P)->ancount) + 1);

			P->memo.an.end = P->end;
			P->memo.ns.base = P->end;
			P->memo.ns.end = P->end;
			P->memo.ar.base = P->end;
			P->memo.ar.end = P->end;

			break;
		case DNS_S_NS:
			if (dns_p_count(P, DNS_S_AR)) goto order;

			if (!P->memo.ns.base && (error = dns_p_study(P))) goto error;

			dns_header(P)->nscount = htons(ntohs(dns_header(P)->nscount) + 1);

			P->memo.ns.end = P->end;
			P->memo.ar.base = P->end;
			P->memo.ar.end = P->end;

			break;
		case DNS_S_AR:
			if (!P->memo.ar.base && (error = dns_p_study(P))) goto error;

			dns_header(P)->arcount = htons(ntohs(dns_header(P)->arcount) + 1);

			P->memo.ar.end = P->end;

			if (type == DNS_T_OPT && !P->memo.opt.p) {
				P->memo.opt.p = end;
				P->memo.opt.maxudp = class;
				P->memo.opt.ttl = ttl;
			}

			break;
		default:
			error = DNS_ESECTION;

			goto error;
	} /* switch() */

	return 0;
nobufs:
	error = DNS_ENOBUFS;

	goto error;
order:
	error = DNS_EORDER;

	goto error;
error:
	P->end = end;

	return error;
} /* dns_p_push() */

static void dns_p_dump3(struct dns_packet *P, struct dns_rr_i *I, FILE *fp) {
	enum dns_section section;
	struct dns_rr rr;
	int error;
	union dns_any any;
	char pretty[sizeof any * 2];
	size_t len;

	fputs(";; [HEADER]\n", fp);
	fprintf(fp, ";;    qid : %d\n", ntohs(dns_header(P)->qid));
	fprintf(fp, ";;     qr : %s(%d)\n", (dns_header(P)->qr) ? "RESPONSE" : "QUERY", dns_header(P)->qr);
	fprintf(fp, ";; opcode : %s(%d)\n", dns_stropcode(dns_header(P)->opcode), dns_header(P)->opcode);
	fprintf(fp, ";;     aa : %s(%d)\n", (dns_header(P)->aa) ? "AUTHORITATIVE" : "NON-AUTHORITATIVE", dns_header(P)->aa);
	fprintf(fp, ";;     tc : %s(%d)\n", (dns_header(P)->tc) ? "TRUNCATED" : "NOT-TRUNCATED", dns_header(P)->tc);
	fprintf(fp, ";;     rd : %s(%d)\n", (dns_header(P)->rd) ? "RECURSION-DESIRED" : "RECURSION-NOT-DESIRED",
	        dns_header(P)->rd);
	fprintf(fp, ";;     ra : %s(%d)\n", (dns_header(P)->ra) ? "RECURSION-ALLOWED" : "RECURSION-NOT-ALLOWED",
	        dns_header(P)->ra);
	fprintf(fp, ";;  rcode : %s(%d)\n", dns_strrcode(dns_p_rcode(P)), dns_p_rcode(P));

	section = 0;

	while (dns_rr_grep(&rr, 1, I, P, &error)) {
		if (section != rr.section)
			fprintf(fp, "\n;; [%s:%d]\n", dns_strsection(rr.section), dns_p_count(P, rr.section));

		if ((len = dns_rr_print(pretty, sizeof pretty, &rr, P, &error))) fprintf(fp, "%s\n", pretty);

		section = rr.section;
	}
} /* dns_p_dump3() */

void dns_p_dump(struct dns_packet *P, FILE *fp) {
	dns_p_dump3(P, dns_rr_i_new(P, .section = 0), fp);
} /* dns_p_dump() */

static void dns_s_unstudy(struct dns_s_memo *m) {
	m->base = 0;
	m->end = 0;
}

static void dns_m_unstudy(struct dns_p_memo *m) {
	dns_s_unstudy(&m->qd);
	dns_s_unstudy(&m->an);
	dns_s_unstudy(&m->ns);
	dns_s_unstudy(&m->ar);
	m->opt.p = 0;
	m->opt.maxudp = 0;
	m->opt.ttl = 0;
} /* dns_m_unstudy() */

static int dns_s_study(struct dns_s_memo *m, enum dns_section section, unsigned short base, struct dns_packet *P) {
	unsigned short count, rp;

	count = dns_p_count(P, section);

	for (rp = base; count && rp < P->end; count--)
		rp = dns_rr_skip(rp, P);

	m->base = base;
	m->end = rp;

	return 0;
} /* dns_s_study() */

static int dns_m_study(struct dns_p_memo *m, struct dns_packet *P) {
	struct dns_rr rr;
	int error;

	if ((error = dns_s_study(&m->qd, DNS_S_QD, 12, P))) goto error;
	if ((error = dns_s_study(&m->an, DNS_S_AN, m->qd.end, P))) goto error;
	if ((error = dns_s_study(&m->ns, DNS_S_NS, m->an.end, P))) goto error;
	if ((error = dns_s_study(&m->ar, DNS_S_AR, m->ns.end, P))) goto error;

	m->opt.p = 0;
	m->opt.maxudp = 0;
	m->opt.ttl = 0;
	dns_rr_foreach(&rr, P, .type = DNS_T_OPT, .section = DNS_S_AR) {
		m->opt.p = rr.dn.p;
		m->opt.maxudp = rr.class;
		m->opt.ttl = rr.ttl;
		break;
	}

	return 0;
error:
	dns_m_unstudy(m);

	return error;
} /* dns_m_study() */

int dns_p_study(struct dns_packet *P) {
	return dns_m_study(&P->memo, P);
} /* dns_p_study() */

enum dns_rcode dns_p_rcode(struct dns_packet *P) {
	return 0xfff & ((P->memo.opt.ttl >> 20) | dns_header(P)->rcode);
} /* dns_p_rcode() */

/*
 * Q U E R Y  P A C K E T  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#define DNS_Q_RD 0x1    /* recursion desired */
#define DNS_Q_EDNS0 0x2 /* include OPT RR */

static dns_error_t dns_q_make2(
    struct dns_packet **_Q, const char *qname, size_t qlen, enum dns_type qtype, enum dns_class qclass, int qflags) {
	struct dns_packet *Q = NULL;
	int error;

	if (dns_p_movptr(&Q, _Q)) {
		dns_p_reset(Q);
	} else if (!(Q = dns_p_make(DNS_P_QBUFSIZ, &error))) {
		goto error;
	}

	if ((error = dns_p_push(Q, DNS_S_QD, qname, qlen, qtype, qclass, 0, 0))) goto error;

	dns_header(Q)->rd = !!(qflags & DNS_Q_RD);

	if (qflags & DNS_Q_EDNS0) {
		struct dns_opt opt = DNS_OPT_INIT(&opt);

		opt.version = 0; /* RFC 6891 version */
		opt.maxudp = 4096;

		if ((error = dns_p_push(Q, DNS_S_AR, ".", 1, DNS_T_OPT, dns_opt_class(&opt), dns_opt_ttl(&opt), &opt)))
			goto error;
	}

	*_Q = Q;

	return 0;
error:
	dns_p_free(Q);

	return error;
}

static dns_error_t
dns_q_make(struct dns_packet **Q, const char *qname, enum dns_type qtype, enum dns_class qclass, int qflags) {
	return dns_q_make2(Q, qname, strlen(qname), qtype, qclass, qflags);
}

static dns_error_t dns_q_remake(struct dns_packet **Q, int qflags) {
	char qname[DNS_D_MAXNAME + 1];
	size_t qlen;
	struct dns_rr rr;
	int error;

	assert(Q && *Q);
	if ((error = dns_rr_parse(&rr, 12, *Q))) return error;
	if (!(qlen = dns_d_expand(qname, sizeof qname, rr.dn.p, *Q, &error))) return error;
	if (qlen >= sizeof qname) return DNS_EILLEGAL;
	return dns_q_make2(Q, qname, qlen, rr.type, rr.class, qflags);
}

/*
 * D O M A I N  N A M E  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#ifndef DNS_D_MAXPTRS
#define DNS_D_MAXPTRS 127 /* Arbitrary; possible, valid depth is something like packet size / 2 + fudge. */
#endif

static size_t dns_l_expand(
    unsigned char *dst, size_t lim, unsigned short src, unsigned short *nxt, const unsigned char *data, size_t end) {
	unsigned short len;
	unsigned nptrs = 0;

retry:
	if (src >= end) goto invalid;

	switch (0x03 & (data[src] >> 6)) {
		case 0x00:
			len = (0x3f & (data[src++]));

			if (end - src < len) goto invalid;

			if (lim > 0) {
				memcpy(dst, &data[src], DNS_PP_MIN(lim, len));

				dst[DNS_PP_MIN(lim - 1, len)] = '\0';
			}

			*nxt = src + len;

			return len;
		case 0x01:
			goto invalid;
		case 0x02:
			goto invalid;
		case 0x03:
			if (++nptrs > DNS_D_MAXPTRS) goto invalid;

			if (end - src < 2) goto invalid;

			src = ((0x3f & data[src + 0]) << 8) | ((0xff & data[src + 1]) << 0);

			goto retry;
	} /* switch() */

	/* NOT REACHED */
invalid:
	*nxt = end;

	return 0;
} /* dns_l_expand() */

static unsigned short dns_l_skip(unsigned short src, const unsigned char *data, size_t end) {
	unsigned short len;

	if (src >= end) goto invalid;

	switch (0x03 & (data[src] >> 6)) {
		case 0x00:
			len = (0x3f & (data[src++]));

			if (end - src < len) goto invalid;

			return (len) ? src + len : end;
		case 0x01:
			goto invalid;
		case 0x02:
			goto invalid;
		case 0x03:
			return end;
	} /* switch() */

	/* NOT REACHED */
invalid:
	return end;
} /* dns_l_skip() */

static size_t dns_d_trim(void *dst_, size_t lim, const void *src_, size_t len, int flags) {
	unsigned char *dst = dst_;
	const unsigned char *src = src_;
	size_t dp = 0, sp = 0;
	int lc;

	/* trim any leading dot(s) */
	while (sp < len && src[sp] == '.')
		sp++;

	for (lc = 0; sp < len; lc = src[sp++]) {
		/* trim extra dot(s) */
		if (src[sp] == '.' && lc == '.') continue;

		if (dp < lim) dst[dp] = src[sp];

		dp++;
	}

	if ((flags & DNS_D_ANCHOR) && lc != '.') {
		if (dp < lim) dst[dp] = '.';

		dp++;
	}

	if (lim > 0) dst[DNS_PP_MIN(dp, lim - 1)] = '\0';

	return dp;
} /* dns_d_trim() */

char *dns_d_init(void *dst, size_t lim, const void *src, size_t len, int flags) {
	if (flags & DNS_D_TRIM) {
		dns_d_trim(dst, lim, src, len, flags);
	}
	if (flags & DNS_D_ANCHOR) {
		dns_d_anchor(dst, lim, src, len);
	} else {
		memmove(dst, src, DNS_PP_MIN(lim, len));

		if (lim > 0) ((char *)dst)[DNS_PP_MIN(len, lim - 1)] = '\0';
	}

	return dst;
} /* dns_d_init() */

size_t dns_d_anchor(void *dst, size_t lim, const void *src, size_t len) {
	if (len == 0) return 0;

	memmove(dst, src, DNS_PP_MIN(lim, len));

	if (((const char *)src)[len - 1] != '.') {
		if (len < lim) ((char *)dst)[len] = '.';
		len++;
	}

	if (lim > 0) ((char *)dst)[DNS_PP_MIN(lim - 1, len)] = '\0';

	return len;
} /* dns_d_anchor() */

size_t dns_d_cleave(void *dst, size_t lim, const void *src, size_t len) {
	const char *dot;

	/* XXX: Skip any leading dot. Handles cleaving root ".". */
	if (len == 0 || !(dot = memchr((const char *)src + 1, '.', len - 1))) return 0;

	len -= dot - (const char *)src;

	/* XXX: Unless root, skip the label's trailing dot. */
	if (len > 1) {
		src = ++dot;
		len--;
	} else src = dot;

	memmove(dst, src, DNS_PP_MIN(lim, len));

	if (lim > 0) ((char *)dst)[DNS_PP_MIN(lim - 1, len)] = '\0';

	return len;
} /* dns_d_cleave() */

size_t dns_d_comp(void *dst_, size_t lim, const void *src_, size_t len, struct dns_packet *P, int *error) {
	struct {
		unsigned char *b;
		size_t p, x;
	} dst, src;
	unsigned char ch = '.';

	dst.b = dst_;
	dst.p = 0;
	dst.x = 1;

	src.b = (unsigned char *)src_;
	src.p = 0;
	src.x = 0;

	while (src.x < len) {
		ch = src.b[src.x];

		if (ch == '.') {
			if (dst.p < lim) dst.b[dst.p] = (0x3f & (src.x - src.p));

			dst.p = dst.x++;
			src.p = ++src.x;
		} else {
			if (dst.x < lim) dst.b[dst.x] = ch;

			dst.x++;
			src.x++;
		}
	} /* while() */

	if (src.x > src.p) {
		if (dst.p < lim) dst.b[dst.p] = (0x3f & (src.x - src.p));

		dst.p = dst.x;
	}

	if (dst.p > 1) {
		if (dst.p < lim) dst.b[dst.p] = 0x00;

		dst.p++;
	}

#if 1
	if (dst.p < lim) {
		struct {
			unsigned char label[DNS_D_MAXLABEL + 1];
			size_t len;
			unsigned short p, x, y;
		} a, b;
		unsigned i;

		a.p = 0;

		while ((a.len = dns_l_expand(a.label, sizeof a.label, a.p, &a.x, dst.b, lim))) {
			for (i = 0; i < lengthof(P->dict) && P->dict[i]; i++) {
				b.p = P->dict[i];

				while ((b.len = dns_l_expand(b.label, sizeof b.label, b.p, &b.x, P->data, P->end))) {
					a.y = a.x;
					b.y = b.x;

					while (a.len && b.len && 0 == strcasecmp((char *)a.label, (char *)b.label)) {
						a.len = dns_l_expand(a.label, sizeof a.label, a.y, &a.y, dst.b, lim);
						b.len = dns_l_expand(b.label, sizeof b.label, b.y, &b.y, P->data, P->end);
					}

					if (a.len == 0 && b.len == 0 && b.p <= 0x3fff) {
						dst.b[a.p++] = 0xc0 | (0x3f & (b.p >> 8));
						dst.b[a.p++] = (0xff & (b.p >> 0));

						/* silence static analyzers */
						dns_assume(a.p > 0);

						return a.p;
					}

					b.p = b.x;
				} /* while() */
			}     /* for() */

			a.p = a.x;
		} /* while() */
	}     /* if () */
#endif

	if (!dst.p) *error = DNS_EILLEGAL;

	return dst.p;
} /* dns_d_comp() */

unsigned short dns_d_skip(unsigned short src, struct dns_packet *P) {
	unsigned short len;

	while (src < P->end) {
		switch (0x03 & (P->data[src] >> 6)) {
			case 0x00: /* FOLLOWS */
				len = (0x3f & P->data[src++]);

				if (0 == len) {
					/* success ==> */ return src;
				} else if (P->end - src > len) {
					src += len;

					break;
				} else goto invalid;

				/* NOT REACHED */
			case 0x01: /* RESERVED */
				goto invalid;
			case 0x02: /* RESERVED */
				goto invalid;
			case 0x03: /* POINTER */
				if (P->end - src < 2) goto invalid;

				src += 2;

				/* success ==> */ return src;
		} /* switch() */
	}     /* while() */

invalid:
	return P->end;
} /* dns_d_skip() */

#include <stdio.h>

size_t dns_d_expand(void *dst, size_t lim, unsigned short src, struct dns_packet *P, int *error) {
	size_t dstp = 0;
	unsigned nptrs = 0;
	unsigned char len;

	while (src < P->end) {
		switch ((0x03 & (P->data[src] >> 6))) {
			case 0x00: /* FOLLOWS */
				len = (0x3f & P->data[src]);

				if (0 == len) {
					if (dstp == 0) {
						if (dstp < lim) ((unsigned char *)dst)[dstp] = '.';

						dstp++;
					}

					/* NUL terminate */
					if (lim > 0) ((unsigned char *)dst)[DNS_PP_MIN(dstp, lim - 1)] = '\0';

					/* success ==> */ return dstp;
				}

				src++;

				if (P->end - src < len) goto toolong;

				if (dstp < lim) memcpy(&((unsigned char *)dst)[dstp], &P->data[src], DNS_PP_MIN(len, lim - dstp));

				src += len;
				dstp += len;

				if (dstp < lim) ((unsigned char *)dst)[dstp] = '.';

				dstp++;

				nptrs = 0;

				continue;
			case 0x01: /* RESERVED */
				goto reserved;
			case 0x02: /* RESERVED */
				goto reserved;
			case 0x03: /* POINTER */
				if (++nptrs > DNS_D_MAXPTRS) goto toolong;

				if (P->end - src < 2) goto toolong;

				src = ((0x3f & P->data[src + 0]) << 8) | ((0xff & P->data[src + 1]) << 0);

				continue;
		} /* switch() */
	}     /* while() */

toolong:
	*error = DNS_EILLEGAL;

	if (lim > 0) ((unsigned char *)dst)[DNS_PP_MIN(dstp, lim - 1)] = '\0';

	return 0;
reserved:
	*error = DNS_EILLEGAL;

	if (lim > 0) ((unsigned char *)dst)[DNS_PP_MIN(dstp, lim - 1)] = '\0';

	return 0;
} /* dns_d_expand() */

int dns_d_push(struct dns_packet *P, const void *dn, size_t len) {
	size_t lim = P->size - P->end;
	unsigned dp = P->end;
	int error = DNS_EILLEGAL; /* silence compiler */

	len = dns_d_comp(&P->data[dp], lim, dn, len, P, &error);

	if (len == 0) return error;
	if (len > lim) return DNS_ENOBUFS;

	P->end += len;

	dns_p_dictadd(P, dp);

	return 0;
} /* dns_d_push() */

size_t dns_d_cname(void *dst, size_t lim, const void *dn, size_t len, struct dns_packet *P, int *error_) {
	char host[DNS_D_MAXNAME + 1];
	struct dns_rr_i i;
	struct dns_rr rr;
	unsigned depth;
	int error;

	if (sizeof host <= dns_d_anchor(host, sizeof host, dn, len)) {
		error = ENAMETOOLONG;
		goto error;
	}

	for (depth = 0; depth < 7; depth++) {
		dns_rr_i_init(memset(&i, 0, sizeof i), P);

		i.section = DNS_S_ALL & ~DNS_S_QD;
		i.name = host;
		i.type = DNS_T_CNAME;

		if (!dns_rr_grep(&rr, 1, &i, P, &error)) break;

		if ((error = dns_cname_parse((struct dns_cname *)host, &rr, P))) goto error;
	}

	return dns_strlcpy(dst, host, lim);
error:
	*error_ = error;

	return 0;
} /* dns_d_cname() */

/*
 * R E S O U R C E  R E C O R D  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

int dns_rr_copy(struct dns_packet *P, struct dns_rr *rr, struct dns_packet *Q) {
	unsigned char dn[DNS_D_MAXNAME + 1];
	union dns_any any;
	size_t len;
	int error;

	if (!(len = dns_d_expand(dn, sizeof dn, rr->dn.p, Q, &error))) return error;
	else if (len >= sizeof dn) return DNS_EILLEGAL;

	if (rr->section != DNS_S_QD && (error = dns_any_parse(dns_any_init(&any, sizeof any), rr, Q))) return error;

	return dns_p_push(P, rr->section, dn, len, rr->type, rr->class, rr->ttl, &any);
} /* dns_rr_copy() */

int dns_rr_parse(struct dns_rr *rr, unsigned short src, struct dns_packet *P) {
	unsigned short p = src;

	if (src >= P->end) goto invalid;

	rr->dn.p = p;
	rr->dn.len = (p = dns_d_skip(p, P)) - rr->dn.p;

	if (P->end - p < 4) goto invalid;

	rr->type = ((0xff & P->data[p + 0]) << 8) | ((0xff & P->data[p + 1]) << 0);

	rr->class = ((0xff & P->data[p + 2]) << 8) | ((0xff & P->data[p + 3]) << 0);

	p += 4;

	if (src < dns_p_qend(P)) {
		rr->section = DNS_S_QUESTION;

		rr->ttl = 0;
		rr->rd.p = 0;
		rr->rd.len = 0;

		return 0;
	}

	if (P->end - p < 4) goto invalid;

	rr->ttl = ((0xff & P->data[p + 0]) << 24) | ((0xff & P->data[p + 1]) << 16) | ((0xff & P->data[p + 2]) << 8) |
	          ((0xff & P->data[p + 3]) << 0);
	if (rr->type != DNS_T_OPT) rr->ttl = DNS_PP_MIN(rr->ttl, 0x7fffffffU);

	p += 4;

	if (P->end - p < 2) goto invalid;

	rr->rd.len = ((0xff & P->data[p + 0]) << 8) | ((0xff & P->data[p + 1]) << 0);
	rr->rd.p = p + 2;

	p += 2;

	if (P->end - p < rr->rd.len) goto invalid;

	return 0;
invalid:
	return DNS_EILLEGAL;
} /* dns_rr_parse() */

static unsigned short dns_rr_len(const unsigned short src, struct dns_packet *P) {
	unsigned short rp, rdlen;

	rp = dns_d_skip(src, P);

	if (P->end - rp < 4) return P->end - src;

	rp += 4; /* TYPE, CLASS */

	if (rp <= dns_p_qend(P)) return rp - src;

	if (P->end - rp < 6) return P->end - src;

	rp += 6; /* TTL, RDLEN */

	rdlen = ((0xff & P->data[rp - 2]) << 8) | ((0xff & P->data[rp - 1]) << 0);

	if (P->end - rp < rdlen) return P->end - src;

	rp += rdlen;

	return rp - src;
} /* dns_rr_len() */

unsigned short dns_rr_skip(unsigned short src, struct dns_packet *P) {
	return src + dns_rr_len(src, P);
} /* dns_rr_skip() */

static enum dns_section dns_rr_section(unsigned short src, struct dns_packet *P) {
	enum dns_section section;
	unsigned count, index;
	unsigned short rp;

	if (src >= P->memo.qd.base && src < P->memo.qd.end) return DNS_S_QD;
	if (src >= P->memo.an.base && src < P->memo.an.end) return DNS_S_AN;
	if (src >= P->memo.ns.base && src < P->memo.ns.end) return DNS_S_NS;
	if (src >= P->memo.ar.base && src < P->memo.ar.end) return DNS_S_AR;

	/* NOTE: Possibly bad memoization. Try it the hard-way. */

	for (rp = 12, index = 0; rp < src && rp < P->end; index++)
		rp = dns_rr_skip(rp, P);

	section = DNS_S_QD;
	count = dns_p_count(P, section);

	while (index >= count && section <= DNS_S_AR) {
		section <<= 1;
		count += dns_p_count(P, section);
	}

	return DNS_S_ALL & section;
} /* dns_rr_section() */

static enum dns_type dns_rr_type(unsigned short src, struct dns_packet *P) {
	struct dns_rr rr;
	int error;

	if ((error = dns_rr_parse(&rr, src, P))) return 0;

	return rr.type;
} /* dns_rr_type() */

int dns_rr_cmp(struct dns_rr *r0, struct dns_packet *P0, struct dns_rr *r1, struct dns_packet *P1) {
	char host0[DNS_D_MAXNAME + 1], host1[DNS_D_MAXNAME + 1];
	union dns_any any0, any1;
	int cmp, error;
	size_t len;

	if ((cmp = r0->type - r1->type)) return cmp;

	if ((cmp = r0->class - r1->class)) return cmp;

	/*
	 * FIXME: Do label-by-label comparison to handle illegally long names?
	 */

	if (!(len = dns_d_expand(host0, sizeof host0, r0->dn.p, P0, &error)) || len >= sizeof host0) return -1;

	if (!(len = dns_d_expand(host1, sizeof host1, r1->dn.p, P1, &error)) || len >= sizeof host1) return 1;

	if ((cmp = strcasecmp(host0, host1))) return cmp;

	if (DNS_S_QD & (r0->section | r1->section)) {
		if (r0->section == r1->section) return 0;

		return (r0->section == DNS_S_QD) ? -1 : 1;
	}

	if ((error = dns_any_parse(&any0, r0, P0))) return -1;

	if ((error = dns_any_parse(&any1, r1, P1))) return 1;

	return dns_any_cmp(&any0, r0->type, &any1, r1->type);
} /* dns_rr_cmp() */

static _Bool dns_rr_exists(struct dns_rr *rr0, struct dns_packet *P0, struct dns_packet *P1) {
	struct dns_rr rr1;

	dns_rr_foreach(&rr1, P1, .section = rr0->section, .type = rr0->type) {
		if (0 == dns_rr_cmp(rr0, P0, &rr1, P1)) return 1;
	}

	return 0;
} /* dns_rr_exists() */

static unsigned short dns_rr_offset(struct dns_rr *rr) {
	return rr->dn.p;
} /* dns_rr_offset() */

static _Bool dns_rr_i_match(struct dns_rr *rr, struct dns_rr_i *i, struct dns_packet *P) {
	if (i->section && !(rr->section & i->section)) return 0;

	if (i->type && rr->type != i->type && i->type != DNS_T_ALL) return 0;

	if (i->class && rr->class != i->class && i->class != DNS_C_ANY) return 0;

	if (i->name) {
		char dn[DNS_D_MAXNAME + 1];
		size_t len;
		int error;

		if (!(len = dns_d_expand(dn, sizeof dn, rr->dn.p, P, &error)) || len >= sizeof dn) return 0;

		if (0 != strcasecmp(dn, i->name)) return 0;
	}

	if (i->data && i->type && rr->section > DNS_S_QD) {
		union dns_any rd;
		int error;

		if ((error = dns_any_parse(&rd, rr, P))) return 0;

		if (0 != dns_any_cmp(&rd, rr->type, i->data, i->type)) return 0;
	}

	return 1;
} /* dns_rr_i_match() */

static unsigned short dns_rr_i_start(struct dns_rr_i *i, struct dns_packet *P) {
	unsigned short rp;
	struct dns_rr r0, rr;
	int error;

	if ((i->section & DNS_S_QD) && P->memo.qd.base) rp = P->memo.qd.base;
	else if ((i->section & DNS_S_AN) && P->memo.an.base) rp = P->memo.an.base;
	else if ((i->section & DNS_S_NS) && P->memo.ns.base) rp = P->memo.ns.base;
	else if ((i->section & DNS_S_AR) && P->memo.ar.base) rp = P->memo.ar.base;
	else rp = 12;

	for (; rp < P->end; rp = dns_rr_skip(rp, P)) {
		if ((error = dns_rr_parse(&rr, rp, P))) continue;

		rr.section = dns_rr_section(rp, P);

		if (!dns_rr_i_match(&rr, i, P)) continue;

		r0 = rr;

		goto lower;
	}

	return P->end;
lower:
	if (i->sort == &dns_rr_i_packet) return dns_rr_offset(&r0);

	while ((rp = dns_rr_skip(rp, P)) < P->end) {
		if ((error = dns_rr_parse(&rr, rp, P))) continue;

		rr.section = dns_rr_section(rp, P);

		if (!dns_rr_i_match(&rr, i, P)) continue;

		if (i->sort(&rr, &r0, i, P) < 0) r0 = rr;
	}

	return dns_rr_offset(&r0);
} /* dns_rr_i_start() */

static unsigned short dns_rr_i_skip(unsigned short rp, struct dns_rr_i *i, struct dns_packet *P) {
	struct dns_rr r0, r1, rr;
	int error;

	if ((error = dns_rr_parse(&r0, rp, P))) return P->end;

	r0.section = dns_rr_section(rp, P);

	rp = (i->sort == &dns_rr_i_packet) ? dns_rr_skip(rp, P) : 12;

	for (; rp < P->end; rp = dns_rr_skip(rp, P)) {
		if ((error = dns_rr_parse(&rr, rp, P))) continue;

		rr.section = dns_rr_section(rp, P);

		if (!dns_rr_i_match(&rr, i, P)) continue;

		if (i->sort(&rr, &r0, i, P) <= 0) continue;

		r1 = rr;

		goto lower;
	}

	return P->end;
lower:
	if (i->sort == &dns_rr_i_packet) return dns_rr_offset(&r1);

	while ((rp = dns_rr_skip(rp, P)) < P->end) {
		if ((error = dns_rr_parse(&rr, rp, P))) continue;

		rr.section = dns_rr_section(rp, P);

		if (!dns_rr_i_match(&rr, i, P)) continue;

		if (i->sort(&rr, &r0, i, P) <= 0) continue;

		if (i->sort(&rr, &r1, i, P) >= 0) continue;

		r1 = rr;
	}

	return dns_rr_offset(&r1);
} /* dns_rr_i_skip() */

int dns_rr_i_packet(struct dns_rr *a, struct dns_rr *b, struct dns_rr_i *i, struct dns_packet *P) {
	(void)i;
	(void)P;

	return (int)a->dn.p - (int)b->dn.p;
} /* dns_rr_i_packet() */

int dns_rr_i_order(struct dns_rr *a, struct dns_rr *b, struct dns_rr_i *i, struct dns_packet *P) {
	int cmp;

	(void)i;

	if ((cmp = a->section - b->section)) return cmp;

	if (a->type != b->type) return (int)a->dn.p - (int)b->dn.p;

	return dns_rr_cmp(a, P, b, P);
} /* dns_rr_i_order() */

int dns_rr_i_shuffle(struct dns_rr *a, struct dns_rr *b, struct dns_rr_i *i, struct dns_packet *P) {
	int cmp;

	(void)i;
	(void)P;

	while (!i->state.regs[0])
		i->state.regs[0] = dns_random();

	if ((cmp = a->section - b->section)) return cmp;

	return dns_k_shuffle16(a->dn.p, i->state.regs[0]) - dns_k_shuffle16(b->dn.p, i->state.regs[0]);
} /* dns_rr_i_shuffle() */

struct dns_rr_i *dns_rr_i_init(struct dns_rr_i *i, struct dns_packet *P) {
	static const struct dns_rr_i i_initializer;

	(void)P;

	i->state = i_initializer.state;
	i->saved = i->state;

	return i;
} /* dns_rr_i_init() */

unsigned dns_rr_grep(struct dns_rr *rr, unsigned lim, struct dns_rr_i *i, struct dns_packet *P, int *error_) {
	unsigned count = 0;
	int error;

	switch (i->state.exec) {
		case 0:
			if (!i->sort) i->sort = &dns_rr_i_packet;

			i->state.next = dns_rr_i_start(i, P);
			i->state.exec++;

			/* FALL THROUGH */
		case 1:
			while (count < lim && i->state.next < P->end) {
				if ((error = dns_rr_parse(rr, i->state.next, P))) goto error;

				rr->section = dns_rr_section(i->state.next, P);

				rr++;
				count++;
				i->state.count++;

				i->state.next = dns_rr_i_skip(i->state.next, i, P);
			} /* while() */

			break;
	} /* switch() */

	return count;
error:
	*error_ = error;

	return count;
} /* dns_rr_grep() */

size_t dns_rr_print(void *_dst, size_t lim, struct dns_rr *rr, struct dns_packet *P, int *_error) {
	struct dns_buf dst = DNS_B_INTO(_dst, lim);
	union dns_any any;
	size_t n;
	int error;

	if (rr->section == DNS_S_QD) dns_b_putc(&dst, ';');

	if (!(n = dns_d_expand(any.ns.host, sizeof any.ns.host, rr->dn.p, P, &error))) goto error;
	dns_b_put(&dst, any.ns.host, DNS_PP_MIN(n, sizeof any.ns.host - 1));

	if (rr->section != DNS_S_QD) {
		dns_b_putc(&dst, ' ');
		dns_b_fmtju(&dst, rr->ttl, 0);
	}

	dns_b_putc(&dst, ' ');
	dns_b_puts(&dst, dns_strclass(rr->class));
	dns_b_putc(&dst, ' ');
	dns_b_puts(&dst, dns_strtype(rr->type));

	if (rr->section == DNS_S_QD) goto epilog;

	dns_b_putc(&dst, ' ');

	if ((error = dns_any_parse(dns_any_init(&any, sizeof any), rr, P))) goto error;

	n = dns_any_print(dst.p, dst.pe - dst.p, &any, rr->type);
	dst.p += DNS_PP_MIN(n, (size_t)(dst.pe - dst.p));
epilog:
	return dns_b_strllen(&dst);
error:
	*_error = error;

	return 0;
} /* dns_rr_print() */

int dns_a_parse(struct dns_a *a, struct dns_rr *rr, struct dns_packet *P) {
	unsigned long addr;

	if (rr->rd.len != 4) return DNS_EILLEGAL;

	addr = ((0xffU & P->data[rr->rd.p + 0]) << 24) | ((0xffU & P->data[rr->rd.p + 1]) << 16) |
	       ((0xffU & P->data[rr->rd.p + 2]) << 8) | ((0xffU & P->data[rr->rd.p + 3]) << 0);

	a->addr.s_addr = htonl(addr);

	return 0;
} /* dns_a_parse() */

int dns_a_push(struct dns_packet *P, struct dns_a *a) {
	unsigned long addr;

	if (P->size - P->end < 6) return DNS_ENOBUFS;

	P->data[P->end++] = 0x00;
	P->data[P->end++] = 0x04;

	addr = ntohl(a->addr.s_addr);

	P->data[P->end++] = 0xffU & (addr >> 24);
	P->data[P->end++] = 0xffU & (addr >> 16);
	P->data[P->end++] = 0xffU & (addr >> 8);
	P->data[P->end++] = 0xffU & (addr >> 0);

	return 0;
} /* dns_a_push() */

size_t dns_a_arpa(void *_dst, size_t lim, const struct dns_a *a) {
	struct dns_buf dst = DNS_B_INTO(_dst, lim);
	unsigned long octets = ntohl(a->addr.s_addr);
	unsigned i;

	for (i = 0; i < 4; i++) {
		dns_b_fmtju(&dst, 0xff & octets, 0);
		dns_b_putc(&dst, '.');
		octets >>= 8;
	}

	dns_b_puts(&dst, "in-addr.arpa.");

	return dns_b_strllen(&dst);
} /* dns_a_arpa() */

int dns_a_cmp(const struct dns_a *a, const struct dns_a *b) {
	if (ntohl(a->addr.s_addr) < ntohl(b->addr.s_addr)) return -1;
	if (ntohl(a->addr.s_addr) > ntohl(b->addr.s_addr)) return 1;

	return 0;
} /* dns_a_cmp() */

size_t dns_a_print(void *dst, size_t lim, struct dns_a *a) {
	char addr[INET_ADDRSTRLEN + 1] = "0.0.0.0";

	dns_inet_ntop(AF_INET, &a->addr, addr, sizeof addr);

	return dns_strlcpy(dst, addr, lim);
} /* dns_a_print() */

int dns_aaaa_parse(struct dns_aaaa *aaaa, struct dns_rr *rr, struct dns_packet *P) {
	if (rr->rd.len != sizeof aaaa->addr.s6_addr) return DNS_EILLEGAL;

	memcpy(aaaa->addr.s6_addr, &P->data[rr->rd.p], sizeof aaaa->addr.s6_addr);

	return 0;
} /* dns_aaaa_parse() */

int dns_aaaa_push(struct dns_packet *P, struct dns_aaaa *aaaa) {
	if (P->size - P->end < 2 + sizeof aaaa->addr.s6_addr) return DNS_ENOBUFS;

	P->data[P->end++] = 0x00;
	P->data[P->end++] = 0x10;

	memcpy(&P->data[P->end], aaaa->addr.s6_addr, sizeof aaaa->addr.s6_addr);

	P->end += sizeof aaaa->addr.s6_addr;

	return 0;
} /* dns_aaaa_push() */

int dns_aaaa_cmp(const struct dns_aaaa *a, const struct dns_aaaa *b) {
	unsigned i;
	int cmp;

	for (i = 0; i < lengthof(a->addr.s6_addr); i++) {
		if ((cmp = (a->addr.s6_addr[i] - b->addr.s6_addr[i]))) return cmp;
	}

	return 0;
} /* dns_aaaa_cmp() */

size_t dns_aaaa_arpa(void *_dst, size_t lim, const struct dns_aaaa *aaaa) {
	static const unsigned char hex[16] = "0123456789abcdef";
	struct dns_buf dst = DNS_B_INTO(_dst, lim);
	unsigned nyble;
	int i, j;

	for (i = sizeof aaaa->addr.s6_addr - 1; i >= 0; i--) {
		nyble = aaaa->addr.s6_addr[i];

		for (j = 0; j < 2; j++) {
			dns_b_putc(&dst, hex[0x0f & nyble]);
			dns_b_putc(&dst, '.');
			nyble >>= 4;
		}
	}

	dns_b_puts(&dst, "ip6.arpa.");

	return dns_b_strllen(&dst);
} /* dns_aaaa_arpa() */

size_t dns_aaaa_print(void *dst, size_t lim, struct dns_aaaa *aaaa) {
	char addr[INET6_ADDRSTRLEN + 1] = "::";

	dns_inet_ntop(AF_INET6, &aaaa->addr, addr, sizeof addr);

	return dns_strlcpy(dst, addr, lim);
} /* dns_aaaa_print() */

int dns_mx_parse(struct dns_mx *mx, struct dns_rr *rr, struct dns_packet *P) {
	size_t len;
	int error;

	if (rr->rd.len < 3) return DNS_EILLEGAL;

	mx->preference = (0xff00 & (P->data[rr->rd.p + 0] << 8)) | (0x00ff & (P->data[rr->rd.p + 1] << 0));

	if (!(len = dns_d_expand(mx->host, sizeof mx->host, rr->rd.p + 2, P, &error))) return error;
	else if (len >= sizeof mx->host) return DNS_EILLEGAL;

	return 0;
} /* dns_mx_parse() */

int dns_mx_push(struct dns_packet *P, struct dns_mx *mx) {
	size_t end, len;
	int error;

	if (P->size - P->end < 5) return DNS_ENOBUFS;

	end = P->end;
	P->end += 2;

	P->data[P->end++] = 0xff & (mx->preference >> 8);
	P->data[P->end++] = 0xff & (mx->preference >> 0);

	if ((error = dns_d_push(P, mx->host, strlen(mx->host)))) goto error;

	len = P->end - end - 2;

	P->data[end + 0] = 0xff & (len >> 8);
	P->data[end + 1] = 0xff & (len >> 0);

	return 0;
error:
	P->end = end;

	return error;
} /* dns_mx_push() */

int dns_mx_cmp(const struct dns_mx *a, const struct dns_mx *b) {
	int cmp;

	if ((cmp = a->preference - b->preference)) return cmp;

	return strcasecmp(a->host, b->host);
} /* dns_mx_cmp() */

size_t dns_mx_print(void *_dst, size_t lim, struct dns_mx *mx) {
	struct dns_buf dst = DNS_B_INTO(_dst, lim);

	dns_b_fmtju(&dst, mx->preference, 0);
	dns_b_putc(&dst, ' ');
	dns_b_puts(&dst, mx->host);

	return dns_b_strllen(&dst);
} /* dns_mx_print() */

size_t dns_mx_cname(void *dst, size_t lim, struct dns_mx *mx) {
	return dns_strlcpy(dst, mx->host, lim);
} /* dns_mx_cname() */

int dns_ns_parse(struct dns_ns *ns, struct dns_rr *rr, struct dns_packet *P) {
	size_t len;
	int error;

	if (!(len = dns_d_expand(ns->host, sizeof ns->host, rr->rd.p, P, &error))) return error;
	else if (len >= sizeof ns->host) return DNS_EILLEGAL;

	return 0;
} /* dns_ns_parse() */

int dns_ns_push(struct dns_packet *P, struct dns_ns *ns) {
	size_t end, len;
	int error;

	if (P->size - P->end < 3) return DNS_ENOBUFS;

	end = P->end;
	P->end += 2;

	if ((error = dns_d_push(P, ns->host, strlen(ns->host)))) goto error;

	len = P->end - end - 2;

	P->data[end + 0] = 0xff & (len >> 8);
	P->data[end + 1] = 0xff & (len >> 0);

	return 0;
error:
	P->end = end;

	return error;
} /* dns_ns_push() */

int dns_ns_cmp(const struct dns_ns *a, const struct dns_ns *b) {
	return strcasecmp(a->host, b->host);
} /* dns_ns_cmp() */

size_t dns_ns_print(void *dst, size_t lim, struct dns_ns *ns) {
	return dns_strlcpy(dst, ns->host, lim);
} /* dns_ns_print() */

size_t dns_ns_cname(void *dst, size_t lim, struct dns_ns *ns) {
	return dns_strlcpy(dst, ns->host, lim);
} /* dns_ns_cname() */

int dns_cname_parse(struct dns_cname *cname, struct dns_rr *rr, struct dns_packet *P) {
	return dns_ns_parse((struct dns_ns *)cname, rr, P);
} /* dns_cname_parse() */

int dns_cname_push(struct dns_packet *P, struct dns_cname *cname) {
	return dns_ns_push(P, (struct dns_ns *)cname);
} /* dns_cname_push() */

int dns_cname_cmp(const struct dns_cname *a, const struct dns_cname *b) {
	return strcasecmp(a->host, b->host);
} /* dns_cname_cmp() */

size_t dns_cname_print(void *dst, size_t lim, struct dns_cname *cname) {
	return dns_ns_print(dst, lim, (struct dns_ns *)cname);
} /* dns_cname_print() */

size_t dns_cname_cname(void *dst, size_t lim, struct dns_cname *cname) {
	return dns_strlcpy(dst, cname->host, lim);
} /* dns_cname_cname() */

int dns_soa_parse(struct dns_soa *soa, struct dns_rr *rr, struct dns_packet *P) {
	struct {
		void *dst;
		size_t lim;
	} dn[] = {{soa->mname, sizeof soa->mname}, {soa->rname, sizeof soa->rname}};
	unsigned *ts[] = {&soa->serial, &soa->refresh, &soa->retry, &soa->expire, &soa->minimum};
	unsigned short rp;
	unsigned i, j, n;
	int error;

	/* MNAME / RNAME */
	if ((rp = rr->rd.p) >= P->end) return DNS_EILLEGAL;

	for (i = 0; i < lengthof(dn); i++) {
		if (!(n = dns_d_expand(dn[i].dst, dn[i].lim, rp, P, &error))) return error;
		else if (n >= dn[i].lim) return DNS_EILLEGAL;

		if ((rp = dns_d_skip(rp, P)) >= P->end) return DNS_EILLEGAL;
	}

	/* SERIAL / REFRESH / RETRY / EXPIRE / MINIMUM */
	for (i = 0; i < lengthof(ts); i++) {
		for (j = 0; j < 4; j++, rp++) {
			if (rp >= P->end) return DNS_EILLEGAL;

			*ts[i] <<= 8;
			*ts[i] |= (0xff & P->data[rp]);
		}
	}

	return 0;
} /* dns_soa_parse() */

int dns_soa_push(struct dns_packet *P, struct dns_soa *soa) {
	void *dn[] = {soa->mname, soa->rname};
	unsigned ts[] = {(0xffffffff & soa->serial), (0x7fffffff & soa->refresh), (0x7fffffff & soa->retry),
	                 (0x7fffffff & soa->expire), (0xffffffff & soa->minimum)};
	unsigned i, j;
	size_t end, len;
	int error;

	end = P->end;

	if ((P->end += 2) >= P->size) goto toolong;

	/* MNAME / RNAME */
	for (i = 0; i < lengthof(dn); i++) {
		if ((error = dns_d_push(P, dn[i], strlen(dn[i])))) goto error;
	}

	/* SERIAL / REFRESH / RETRY / EXPIRE / MINIMUM */
	for (i = 0; i < lengthof(ts); i++) {
		if ((P->end += 4) >= P->size) goto toolong;

		for (j = 1; j <= 4; j++) {
			P->data[P->end - j] = (0xff & ts[i]);
			ts[i] >>= 8;
		}
	}

	len = P->end - end - 2;
	P->data[end + 0] = (0xff & (len >> 8));
	P->data[end + 1] = (0xff & (len >> 0));

	return 0;
toolong:
	error = DNS_ENOBUFS;

	/* FALL THROUGH */
error:
	P->end = end;

	return error;
} /* dns_soa_push() */

int dns_soa_cmp(const struct dns_soa *a, const struct dns_soa *b) {
	int cmp;

	if ((cmp = strcasecmp(a->mname, b->mname))) return cmp;

	if ((cmp = strcasecmp(a->rname, b->rname))) return cmp;

	if (a->serial > b->serial) return -1;
	else if (a->serial < b->serial) return 1;

	if (a->refresh > b->refresh) return -1;
	else if (a->refresh < b->refresh) return 1;

	if (a->retry > b->retry) return -1;
	else if (a->retry < b->retry) return 1;

	if (a->expire > b->expire) return -1;
	else if (a->expire < b->expire) return 1;

	if (a->minimum > b->minimum) return -1;
	else if (a->minimum < b->minimum) return 1;

	return 0;
} /* dns_soa_cmp() */

size_t dns_soa_print(void *_dst, size_t lim, struct dns_soa *soa) {
	struct dns_buf dst = DNS_B_INTO(_dst, lim);

	dns_b_puts(&dst, soa->mname);
	dns_b_putc(&dst, ' ');
	dns_b_puts(&dst, soa->rname);
	dns_b_putc(&dst, ' ');
	dns_b_fmtju(&dst, soa->serial, 0);
	dns_b_putc(&dst, ' ');
	dns_b_fmtju(&dst, soa->refresh, 0);
	dns_b_putc(&dst, ' ');
	dns_b_fmtju(&dst, soa->retry, 0);
	dns_b_putc(&dst, ' ');
	dns_b_fmtju(&dst, soa->expire, 0);
	dns_b_putc(&dst, ' ');
	dns_b_fmtju(&dst, soa->minimum, 0);

	return dns_b_strllen(&dst);
} /* dns_soa_print() */

int dns_srv_parse(struct dns_srv *srv, struct dns_rr *rr, struct dns_packet *P) {
	unsigned short rp;
	unsigned i;
	size_t n;
	int error;

	memset(srv, '\0', sizeof *srv);

	rp = rr->rd.p;

	if (rr->rd.len < 7) return DNS_EILLEGAL;

	for (i = 0; i < 2; i++, rp++) {
		srv->priority <<= 8;
		srv->priority |= (0xff & P->data[rp]);
	}

	for (i = 0; i < 2; i++, rp++) {
		srv->weight <<= 8;
		srv->weight |= (0xff & P->data[rp]);
	}

	for (i = 0; i < 2; i++, rp++) {
		srv->port <<= 8;
		srv->port |= (0xff & P->data[rp]);
	}

	if (!(n = dns_d_expand(srv->target, sizeof srv->target, rp, P, &error))) return error;
	else if (n >= sizeof srv->target) return DNS_EILLEGAL;

	return 0;
} /* dns_srv_parse() */

int dns_srv_push(struct dns_packet *P, struct dns_srv *srv) {
	size_t end, len;
	int error;

	end = P->end;

	if (P->size - P->end < 2) goto toolong;

	P->end += 2;

	if (P->size - P->end < 6) goto toolong;

	P->data[P->end++] = 0xff & (srv->priority >> 8);
	P->data[P->end++] = 0xff & (srv->priority >> 0);

	P->data[P->end++] = 0xff & (srv->weight >> 8);
	P->data[P->end++] = 0xff & (srv->weight >> 0);

	P->data[P->end++] = 0xff & (srv->port >> 8);
	P->data[P->end++] = 0xff & (srv->port >> 0);

	if (0 == (len = dns_d_comp(&P->data[P->end], P->size - P->end, srv->target, strlen(srv->target), P, &error)))
		goto error;
	else if (P->size - P->end < len) goto toolong;

	P->end += len;

	if (P->end > 65535) goto toolong;

	len = P->end - end - 2;

	P->data[end + 0] = 0xff & (len >> 8);
	P->data[end + 1] = 0xff & (len >> 0);

	return 0;
toolong:
	error = DNS_ENOBUFS;

	/* FALL THROUGH */
error:
	P->end = end;

	return error;
} /* dns_srv_push() */

int dns_srv_cmp(const struct dns_srv *a, const struct dns_srv *b) {
	int cmp;

	if ((cmp = a->priority - b->priority)) return cmp;

	/*
	 * FIXME: We need some sort of random seed to implement the dynamic
	 * weighting required by RFC 2782.
	 */
	if ((cmp = a->weight - b->weight)) return cmp;

	if ((cmp = a->port - b->port)) return cmp;

	return strcasecmp(a->target, b->target);
} /* dns_srv_cmp() */

size_t dns_srv_print(void *_dst, size_t lim, struct dns_srv *srv) {
	struct dns_buf dst = DNS_B_INTO(_dst, lim);

	dns_b_fmtju(&dst, srv->priority, 0);
	dns_b_putc(&dst, ' ');
	dns_b_fmtju(&dst, srv->weight, 0);
	dns_b_putc(&dst, ' ');
	dns_b_fmtju(&dst, srv->port, 0);
	dns_b_putc(&dst, ' ');
	dns_b_puts(&dst, srv->target);

	return dns_b_strllen(&dst);
} /* dns_srv_print() */

size_t dns_srv_cname(void *dst, size_t lim, struct dns_srv *srv) {
	return dns_strlcpy(dst, srv->target, lim);
} /* dns_srv_cname() */

unsigned int dns_opt_ttl(const struct dns_opt *opt) {
	unsigned int ttl = 0;

	ttl |= (0xffU & opt->rcode) << 24;
	ttl |= (0xffU & opt->version) << 16;
	ttl |= (0xffffU & opt->flags) << 0;

	return ttl;
} /* dns_opt_ttl() */

unsigned short dns_opt_class(const struct dns_opt *opt) {
	return opt->maxudp;
} /* dns_opt_class() */

struct dns_opt *dns_opt_init(struct dns_opt *opt, size_t size) {
	assert(size >= offsetof(struct dns_opt, data));

	opt->size = size - offsetof(struct dns_opt, data);
	opt->len = 0;

	opt->rcode = 0;
	opt->version = 0;
	opt->maxudp = 0;

	return opt;
} /* dns_opt_init() */

static union dns_any *dns_opt_initany(union dns_any *any, size_t size) {
	return dns_opt_init(&any->opt, size), any;
} /* dns_opt_initany() */

int dns_opt_parse(struct dns_opt *opt, struct dns_rr *rr, struct dns_packet *P) {
	const struct dns_buf src = DNS_B_FROM(&P->data[rr->rd.p], rr->rd.len);
	struct dns_buf dst = DNS_B_INTO(opt->data, opt->size);
	int error;

	opt->rcode = 0xfff & ((rr->ttl >> 20) | dns_header(P)->rcode);
	opt->version = 0xff & (rr->ttl >> 16);
	opt->flags = 0xffff & rr->ttl;
	opt->maxudp = 0xffff & rr->class;

	while (src.p < src.pe) {
		int code, len;

		if (-1 == (code = dns_b_get16(&src, -1))) return src.error;
		if (-1 == (len = dns_b_get16(&src, -1))) return src.error;

		switch (code) {
			default:
				dns_b_put16(&dst, code);
				dns_b_put16(&dst, len);
				if ((error = dns_b_move(&dst, &src, len))) return error;
				break;
		}
	}

	return 0;
} /* dns_opt_parse() */

int dns_opt_push(struct dns_packet *P, struct dns_opt *opt) {
	const struct dns_buf src = DNS_B_FROM(opt->data, opt->len);
	struct dns_buf dst = DNS_B_INTO(&P->data[P->end], (P->size - P->end));
	int error;

	/* rdata length (see below) */
	if ((error = dns_b_put16(&dst, 0))) goto error;

	/* ... push known options here */

	/* push opaque option data */
	if ((error = dns_b_move(&dst, &src, (size_t)(src.pe - src.p)))) goto error;

	/* rdata length */
	if ((error = dns_b_pput16(&dst, dns_b_tell(&dst) - 2, 0))) goto error;

#if !DNS_DEBUG_OPT_FORMERR
	P->end += dns_b_tell(&dst);
#endif

	return 0;
error:
	return error;
} /* dns_opt_push() */

int dns_opt_cmp(const struct dns_opt *a, const struct dns_opt *b) {
	(void)a;
	(void)b;

	return -1;
} /* dns_opt_cmp() */

size_t dns_opt_print(void *_dst, size_t lim, struct dns_opt *opt) {
	struct dns_buf dst = DNS_B_INTO(_dst, lim);
	size_t p;

	dns_b_putc(&dst, '"');

	for (p = 0; p < opt->len; p++) {
		dns_b_putc(&dst, '\\');
		dns_b_fmtju(&dst, opt->data[p], 3);
	}

	dns_b_putc(&dst, '"');

	return dns_b_strllen(&dst);
} /* dns_opt_print() */

int dns_ptr_parse(struct dns_ptr *ptr, struct dns_rr *rr, struct dns_packet *P) {
	return dns_ns_parse((struct dns_ns *)ptr, rr, P);
} /* dns_ptr_parse() */

int dns_ptr_push(struct dns_packet *P, struct dns_ptr *ptr) {
	return dns_ns_push(P, (struct dns_ns *)ptr);
} /* dns_ptr_push() */

size_t dns_ptr_qname(void *dst, size_t lim, int af, void *addr) {
	switch (af) {
		case AF_INET6:
			return dns_aaaa_arpa(dst, lim, addr);
		case AF_INET:
			return dns_a_arpa(dst, lim, addr);
		default:
			return dns_a_arpa(dst, lim, &(struct dns_a){{INADDR_NONE}});
	}
} /* dns_ptr_qname() */

int dns_ptr_cmp(const struct dns_ptr *a, const struct dns_ptr *b) {
	return strcasecmp(a->host, b->host);
} /* dns_ptr_cmp() */

size_t dns_ptr_print(void *dst, size_t lim, struct dns_ptr *ptr) {
	return dns_ns_print(dst, lim, (struct dns_ns *)ptr);
} /* dns_ptr_print() */

size_t dns_ptr_cname(void *dst, size_t lim, struct dns_ptr *ptr) {
	return dns_strlcpy(dst, ptr->host, lim);
} /* dns_ptr_cname() */

int dns_sshfp_parse(struct dns_sshfp *fp, struct dns_rr *rr, struct dns_packet *P) {
	unsigned p = rr->rd.p, pe = rr->rd.p + rr->rd.len;

	if (pe - p < 2) return DNS_EILLEGAL;

	fp->algo = P->data[p++];
	fp->type = P->data[p++];

	switch (fp->type) {
		case DNS_SSHFP_SHA1:
			if (pe - p < sizeof fp->digest.sha1) return DNS_EILLEGAL;

			memcpy(fp->digest.sha1, &P->data[p], sizeof fp->digest.sha1);

			break;
		default:
			break;
	} /* switch() */

	return 0;
} /* dns_sshfp_parse() */

int dns_sshfp_push(struct dns_packet *P, struct dns_sshfp *fp) {
	unsigned p = P->end, pe = P->size, n;

	if (pe - p < 4) return DNS_ENOBUFS;

	p += 2;
	P->data[p++] = 0xff & fp->algo;
	P->data[p++] = 0xff & fp->type;

	switch (fp->type) {
		case DNS_SSHFP_SHA1:
			if (pe - p < sizeof fp->digest.sha1) return DNS_ENOBUFS;

			memcpy(&P->data[p], fp->digest.sha1, sizeof fp->digest.sha1);
			p += sizeof fp->digest.sha1;

			break;
		default:
			return DNS_EILLEGAL;
	} /* switch() */

	n = p - P->end - 2;
	P->data[P->end++] = 0xff & (n >> 8);
	P->data[P->end++] = 0xff & (n >> 0);
	P->end = p;

	return 0;
} /* dns_sshfp_push() */

int dns_sshfp_cmp(const struct dns_sshfp *a, const struct dns_sshfp *b) {
	int cmp;

	if ((cmp = a->algo - b->algo) || (cmp = a->type - b->type)) return cmp;

	switch (a->type) {
		case DNS_SSHFP_SHA1:
			return memcmp(a->digest.sha1, b->digest.sha1, sizeof a->digest.sha1);
		default:
			return 0;
	} /* switch() */

	/* NOT REACHED */
} /* dns_sshfp_cmp() */

size_t dns_sshfp_print(void *_dst, size_t lim, struct dns_sshfp *fp) {
	static const unsigned char hex[16] = "0123456789abcdef";
	struct dns_buf dst = DNS_B_INTO(_dst, lim);
	size_t i;

	dns_b_fmtju(&dst, fp->algo, 0);
	dns_b_putc(&dst, ' ');
	dns_b_fmtju(&dst, fp->type, 0);
	dns_b_putc(&dst, ' ');

	switch (fp->type) {
		case DNS_SSHFP_SHA1:
			for (i = 0; i < sizeof fp->digest.sha1; i++) {
				dns_b_putc(&dst, hex[0x0f & (fp->digest.sha1[i] >> 4)]);
				dns_b_putc(&dst, hex[0x0f & (fp->digest.sha1[i] >> 0)]);
			}

			break;
		default:
			dns_b_putc(&dst, '0');

			break;
	} /* switch() */

	return dns_b_strllen(&dst);
} /* dns_sshfp_print() */

struct dns_txt *dns_txt_init(struct dns_txt *txt, size_t size) {
	assert(size > offsetof(struct dns_txt, data));

	txt->size = size - offsetof(struct dns_txt, data);
	txt->len = 0;

	return txt;
} /* dns_txt_init() */

static union dns_any *dns_txt_initany(union dns_any *any, size_t size) {
	/* NB: union dns_any is already initialized as struct dns_txt */
	(void)size;
	return any;
} /* dns_txt_initany() */

int dns_txt_parse(struct dns_txt *txt, struct dns_rr *rr, struct dns_packet *P) {
	struct {
		unsigned char *b;
		size_t p, end;
	} dst, src;
	unsigned n;

	dst.b = txt->data;
	dst.p = 0;
	dst.end = txt->size;

	src.b = P->data;
	src.p = rr->rd.p;
	src.end = src.p + rr->rd.len;

	while (src.p < src.end) {
		n = 0xff & P->data[src.p++];

		if (src.end - src.p < n || dst.end - dst.p < n) return DNS_EILLEGAL;

		memcpy(&dst.b[dst.p], &src.b[src.p], n);

		dst.p += n;
		src.p += n;
	}

	txt->len = dst.p;

	return 0;
} /* dns_txt_parse() */

int dns_txt_push(struct dns_packet *P, struct dns_txt *txt) {
	struct {
		unsigned char *b;
		size_t p, end;
	} dst, src;
	unsigned n;

	dst.b = P->data;
	dst.p = P->end;
	dst.end = P->size;

	src.b = txt->data;
	src.p = 0;
	src.end = txt->len;

	if (dst.end - dst.p < 2) return DNS_ENOBUFS;

	n = txt->len + ((txt->len + 254) / 255);

	dst.b[dst.p++] = 0xff & (n >> 8);
	dst.b[dst.p++] = 0xff & (n >> 0);

	while (src.p < src.end) {
		n = DNS_PP_MIN(255, src.end - src.p);

		if (dst.p >= dst.end) return DNS_ENOBUFS;

		dst.b[dst.p++] = n;

		if (dst.end - dst.p < n) return DNS_ENOBUFS;

		memcpy(&dst.b[dst.p], &src.b[src.p], n);

		dst.p += n;
		src.p += n;
	}

	P->end = dst.p;

	return 0;
} /* dns_txt_push() */

int dns_txt_cmp(const struct dns_txt *a, const struct dns_txt *b) {
	(void)a;
	(void)b;

	return -1;
} /* dns_txt_cmp() */

size_t dns_txt_print(void *_dst, size_t lim, struct dns_txt *txt) {
	struct dns_buf src = DNS_B_FROM(txt->data, txt->len);
	struct dns_buf dst = DNS_B_INTO(_dst, lim);
	unsigned i;

	if (src.p < src.pe) {
		do {
			dns_b_putc(&dst, '"');

			for (i = 0; i < 256 && src.p < src.pe; i++, src.p++) {
				if (*src.p < 32 || *src.p > 126 || *src.p == '"' || *src.p == '\\') {
					dns_b_putc(&dst, '\\');
					dns_b_fmtju(&dst, *src.p, 3);
				} else {
					dns_b_putc(&dst, *src.p);
				}
			}

			dns_b_putc(&dst, '"');
			dns_b_putc(&dst, ' ');
		} while (src.p < src.pe);

		dns_b_popc(&dst);
	} else {
		dns_b_putc(&dst, '"');
		dns_b_putc(&dst, '"');
	}

	return dns_b_strllen(&dst);
} /* dns_txt_print() */

static const struct dns_rrtype {
	enum dns_type type;
	const char *name;
	union dns_any *(*init)(union dns_any *, size_t);
	int (*parse)();
	int (*push)();
	int (*cmp)();
	size_t (*print)();
	size_t (*cname)();
} dns_rrtypes[] = {
    {
        DNS_T_A,
        "A",
        0,
        &dns_a_parse,
        &dns_a_push,
        &dns_a_cmp,
        &dns_a_print,
        0,
    },
    {
        DNS_T_AAAA,
        "AAAA",
        0,
        &dns_aaaa_parse,
        &dns_aaaa_push,
        &dns_aaaa_cmp,
        &dns_aaaa_print,
        0,
    },
    {
        DNS_T_MX,
        "MX",
        0,
        &dns_mx_parse,
        &dns_mx_push,
        &dns_mx_cmp,
        &dns_mx_print,
        &dns_mx_cname,
    },
    {
        DNS_T_NS,
        "NS",
        0,
        &dns_ns_parse,
        &dns_ns_push,
        &dns_ns_cmp,
        &dns_ns_print,
        &dns_ns_cname,
    },
    {
        DNS_T_CNAME,
        "CNAME",
        0,
        &dns_cname_parse,
        &dns_cname_push,
        &dns_cname_cmp,
        &dns_cname_print,
        &dns_cname_cname,
    },
    {
        DNS_T_SOA,
        "SOA",
        0,
        &dns_soa_parse,
        &dns_soa_push,
        &dns_soa_cmp,
        &dns_soa_print,
        0,
    },
    {
        DNS_T_SRV,
        "SRV",
        0,
        &dns_srv_parse,
        &dns_srv_push,
        &dns_srv_cmp,
        &dns_srv_print,
        &dns_srv_cname,
    },
    {
        DNS_T_OPT,
        "OPT",
        &dns_opt_initany,
        &dns_opt_parse,
        &dns_opt_push,
        &dns_opt_cmp,
        &dns_opt_print,
        0,
    },
    {
        DNS_T_PTR,
        "PTR",
        0,
        &dns_ptr_parse,
        &dns_ptr_push,
        &dns_ptr_cmp,
        &dns_ptr_print,
        &dns_ptr_cname,
    },
    {
        DNS_T_TXT,
        "TXT",
        &dns_txt_initany,
        &dns_txt_parse,
        &dns_txt_push,
        &dns_txt_cmp,
        &dns_txt_print,
        0,
    },
    {
        DNS_T_SPF,
        "SPF",
        &dns_txt_initany,
        &dns_txt_parse,
        &dns_txt_push,
        &dns_txt_cmp,
        &dns_txt_print,
        0,
    },
    {
        DNS_T_SSHFP,
        "SSHFP",
        0,
        &dns_sshfp_parse,
        &dns_sshfp_push,
        &dns_sshfp_cmp,
        &dns_sshfp_print,
        0,
    },
    {
        DNS_T_AXFR,
        "AXFR",
        0,
        0,
        0,
        0,
        0,
        0,
    },
}; /* dns_rrtypes[] */

static const struct dns_rrtype *dns_rrtype(enum dns_type type) {
	const struct dns_rrtype *t;

	for (t = dns_rrtypes; t < endof(dns_rrtypes); t++) {
		if (t->type == type && t->parse) {
			return t;
		}
	}

	return NULL;
} /* dns_rrtype() */

union dns_any *dns_any_init(union dns_any *any, size_t size) {
	dns_static_assert(dns_same_type(any->txt, any->rdata, 1), "unexpected rdata type");
	return (union dns_any *)dns_txt_init(&any->rdata, size);
} /* dns_any_init() */

static size_t dns_any_sizeof(union dns_any *any) {
	dns_static_assert(dns_same_type(any->txt, any->rdata, 1), "unexpected rdata type");
	return offsetof(struct dns_txt, data) + any->rdata.size;
} /* dns_any_sizeof() */

static union dns_any *dns_any_reinit(union dns_any *any, const struct dns_rrtype *t) {
	return (t->init) ? t->init(any, dns_any_sizeof(any)) : any;
} /* dns_any_reinit() */

int dns_any_parse(union dns_any *any, struct dns_rr *rr, struct dns_packet *P) {
	const struct dns_rrtype *t;

	if ((t = dns_rrtype(rr->type))) return t->parse(dns_any_reinit(any, t), rr, P);

	if (rr->rd.len > any->rdata.size) return DNS_EILLEGAL;

	memcpy(any->rdata.data, &P->data[rr->rd.p], rr->rd.len);
	any->rdata.len = rr->rd.len;

	return 0;
} /* dns_any_parse() */

int dns_any_push(struct dns_packet *P, union dns_any *any, enum dns_type type) {
	const struct dns_rrtype *t;

	if ((t = dns_rrtype(type))) return t->push(P, any);

	if (P->size - P->end < any->rdata.len + 2) return DNS_ENOBUFS;

	P->data[P->end++] = 0xff & (any->rdata.len >> 8);
	P->data[P->end++] = 0xff & (any->rdata.len >> 0);

	memcpy(&P->data[P->end], any->rdata.data, any->rdata.len);
	P->end += any->rdata.len;

	return 0;
} /* dns_any_push() */

int dns_any_cmp(const union dns_any *a, enum dns_type x, const union dns_any *b, enum dns_type y) {
	const struct dns_rrtype *t;
	int cmp;

	if ((cmp = x - y)) return cmp;

	if ((t = dns_rrtype(x))) return t->cmp(a, b);

	return -1;
} /* dns_any_cmp() */

size_t dns_any_print(void *_dst, size_t lim, union dns_any *any, enum dns_type type) {
	const struct dns_rrtype *t;
	struct dns_buf src, dst;

	if ((t = dns_rrtype(type))) return t->print(_dst, lim, any);

	dns_b_from(&src, any->rdata.data, any->rdata.len);
	dns_b_into(&dst, _dst, lim);

	dns_b_putc(&dst, '"');

	while (src.p < src.pe) {
		dns_b_putc(&dst, '\\');
		dns_b_fmtju(&dst, *src.p++, 3);
	}

	dns_b_putc(&dst, '"');

	return dns_b_strllen(&dst);
} /* dns_any_print() */

size_t dns_any_cname(void *dst, size_t lim, union dns_any *any, enum dns_type type) {
	const struct dns_rrtype *t;

	if ((t = dns_rrtype(type)) && t->cname) return t->cname(dst, lim, any);

	return 0;
} /* dns_any_cname() */

/*
 * H O S T S  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

struct dns_hosts {
	struct dns_hosts_entry {
		char host[DNS_D_MAXNAME + 1];
		char arpa[73 + 1];

		int af;

		union {
			struct in_addr a4;
			struct in6_addr a6;
		} addr;

		_Bool alias;

		struct dns_hosts_entry *next;
	} *head, **tail;

	dns_atomic_t refcount;
}; /* struct dns_hosts */

struct dns_hosts *dns_hosts_open(int *error) {
	static const struct dns_hosts hosts_initializer = {.refcount = 1};
	struct dns_hosts *hosts;

	if (!(hosts = malloc(sizeof *hosts))) goto syerr;

	*hosts = hosts_initializer;

	hosts->tail = &hosts->head;

	return hosts;
syerr:
	*error = dns_syerr();

	free(hosts);

	return 0;
} /* dns_hosts_open() */

void dns_hosts_close(struct dns_hosts *hosts) {
	struct dns_hosts_entry *ent, *xnt;

	if (!hosts || 1 != dns_hosts_release(hosts)) return;

	for (ent = hosts->head; ent; ent = xnt) {
		xnt = ent->next;

		free(ent);
	}

	free(hosts);

	return;
} /* dns_hosts_close() */

dns_refcount_t dns_hosts_acquire(struct dns_hosts *hosts) {
	return dns_atomic_fetch_add(&hosts->refcount);
} /* dns_hosts_acquire() */

dns_refcount_t dns_hosts_release(struct dns_hosts *hosts) {
	return dns_atomic_fetch_sub(&hosts->refcount);
} /* dns_hosts_release() */

struct dns_hosts *dns_hosts_mortal(struct dns_hosts *hosts) {
	if (hosts) dns_hosts_release(hosts);

	return hosts;
} /* dns_hosts_mortal() */

#if defined(BELLE_SIP_WINDOWS_PHONE) || defined(BELLE_SIP_WINDOWS_UNIVERSAL)
static int dns_hosts_add_localhost(struct dns_hosts *hosts) {
	struct dns_hosts_entry ent;
	memset(&ent, '\0', sizeof(ent));
	ent.af = AF_INET;
	dns_inet_pton(ent.af, "127.0.0.1", &ent.addr);
	dns_d_anchor(ent.host, sizeof(ent.host), "localhost", 9);
	dns_hosts_insert(hosts, ent.af, &ent.addr, ent.host, 0);
	memset(&ent, '\0', sizeof(ent));
	ent.af = AF_INET6;
	dns_inet_pton(ent.af, "::1", &ent.addr);
	dns_d_anchor(ent.host, sizeof(ent.host), "localhost", 9);
	dns_hosts_insert(hosts, ent.af, &ent.addr, ent.host, 1);
	return 0;
}
#endif

struct dns_hosts *dns_hosts_local(int *error_) {
	struct dns_hosts *hosts;
	int error;

	if (!(hosts = dns_hosts_open(&error))) goto error;

#ifdef _WIN32
#if defined(BELLE_SIP_WINDOWS_PHONE) || defined(BELLE_SIP_WINDOWS_UNIVERSAL)
	if ((error = dns_hosts_add_localhost(hosts)))
#else
	if ((error = dns_hosts_loadpath(hosts, "C:/Windows/System32/drivers/etc/hosts")))
#endif
#else
	if ((error = dns_hosts_loadpath(hosts, "/etc/hosts")))
#endif
		goto error;

	return hosts;
error:
	*error_ = error;

	dns_hosts_close(hosts);

	return 0;
} /* dns_hosts_local() */

#define dns_hosts_issep(ch) (dns_isspace(ch))
#define dns_hosts_iscom(ch) ((ch) == '#' || (ch) == ';')

int dns_hosts_loadfile(struct dns_hosts *hosts, FILE *fp) {
	struct dns_hosts_entry ent;
	char word[DNS_PP_MAX(INET6_ADDRSTRLEN, DNS_D_MAXNAME) + 1];
	unsigned wp, wc, skip;
	int ch, error;

	rewind(fp);

	do {
		memset(&ent, '\0', sizeof ent);
		wc = 0;
		skip = 0;

		do {
			memset(word, '\0', sizeof word);
			wp = 0;

			while (EOF != (ch = fgetc(fp)) && ch != '\n') {
				skip |= !!dns_hosts_iscom(ch);

				if (skip) continue;

				if (dns_hosts_issep(ch)) break;

				if (wp < sizeof word - 1) word[wp] = ch;
				wp++;
			}

			if (!wp) continue;

			wc++;

			switch (wc) {
				case 0:
					break;
				case 1:
					ent.af = (strchr(word, ':')) ? AF_INET6 : AF_INET;
					// Normalize some strange IPv4 addresses, eg. 127.1 --> 127.0.0.1
					if (ent.af == AF_INET) {
						int nbdots = 0;
						char *p = word;
						while ((p = strchr(p, '.')) != NULL) {
							nbdots++;
							p++;
						}
						if (nbdots == 1) {
							p = strchr(word, '.');
							p++;
							memmove(p + 4, p, strlen(p));
							memcpy(p, "0.0.", 4);
						}
					}
					skip = (1 != dns_inet_pton(ent.af, word, &ent.addr));

					break;
				default:
					if (!wp) break;

					dns_d_anchor(ent.host, sizeof ent.host, word, wp);

					if ((error = dns_hosts_insert(hosts, ent.af, &ent.addr, ent.host, (wc > 2)))) return error;

					break;
			} /* switch() */
		} while (ch != EOF && ch != '\n');
	} while (ch != EOF);

	return 0;
} /* dns_hosts_loadfile() */

int dns_hosts_loadpath(struct dns_hosts *hosts, const char *path) {
	FILE *fp;
	int error;

	if (!(fp = dns_fopen(path, "rt", &error))) return error;

	error = dns_hosts_loadfile(hosts, fp);

	fclose(fp);

	return error;
} /* dns_hosts_loadpath() */

int dns_hosts_dump(struct dns_hosts *hosts, FILE *fp) {
	struct dns_hosts_entry *ent, *xnt;
	char addr[INET6_ADDRSTRLEN + 1];
	unsigned i;

	for (ent = hosts->head; ent; ent = xnt) {
		xnt = ent->next;

		dns_inet_ntop(ent->af, &ent->addr, addr, sizeof addr);

		fputs(addr, fp);

		for (i = strlen(addr); i < INET_ADDRSTRLEN; i++)
			fputc(' ', fp);

		fputc(' ', fp);

		fputs(ent->host, fp);
		fputc('\n', fp);
	}

	return 0;
} /* dns_hosts_dump() */

int dns_hosts_insert(struct dns_hosts *hosts, int af, const void *addr, const void *host, _Bool alias) {
	struct dns_hosts_entry *ent;
	int error;

	if (!(ent = malloc(sizeof *ent))) goto syerr;

	dns_d_anchor(ent->host, sizeof ent->host, host, strlen(host));

	switch ((ent->af = af)) {
		case AF_INET6:
			memcpy(&ent->addr.a6, addr, sizeof ent->addr.a6);

			dns_aaaa_arpa(ent->arpa, sizeof ent->arpa, addr);

			break;
		case AF_INET:
			memcpy(&ent->addr.a4, addr, sizeof ent->addr.a4);

			dns_a_arpa(ent->arpa, sizeof ent->arpa, addr);

			break;
		default:
			error = EINVAL;

			goto error;
	} /* switch() */

	ent->alias = alias;

	ent->next = 0;
	*hosts->tail = ent;
	hosts->tail = &ent->next;

	return 0;
syerr:
	error = dns_syerr();
error:
	free(ent);

	return error;
} /* dns_hosts_insert() */

int dns_hosts_insert_v4_entry(struct dns_hosts *hosts, const char *ipv4, const char *hostname) {
	struct dns_hosts_entry ent;
	memset(&ent, '\0', sizeof(ent));
	ent.af = AF_INET;
	dns_inet_pton(ent.af, ipv4, &ent.addr);
	dns_d_anchor(ent.host, sizeof(ent.host), hostname, strlen(hostname));
	dns_hosts_insert(hosts, ent.af, &ent.addr, ent.host, 0);
	return 0;
} /*dns_hosts_insert_v4_entry*/

struct dns_packet *dns_hosts_query(struct dns_hosts *hosts, struct dns_packet *Q, int *error_) {
	struct dns_packet *P = dns_p_new(512);
	struct dns_packet *A = 0;
	struct dns_rr rr;
	struct dns_hosts_entry *ent;
	int error, af;
	char qname[DNS_D_MAXNAME + 1];
	size_t qlen;

	if ((error = dns_rr_parse(&rr, 12, Q))) goto error;

	if (!(qlen = dns_d_expand(qname, sizeof qname, rr.dn.p, Q, &error))) goto error;
	else if (qlen >= sizeof qname) goto toolong;

	if ((error = dns_p_push(P, DNS_S_QD, qname, qlen, rr.type, rr.class, 0, 0))) goto error;

	switch (rr.type) {
		case DNS_T_PTR:
			for (ent = hosts->head; ent; ent = ent->next) {
				if (ent->alias || 0 != strcasecmp(qname, ent->arpa)) continue;

				if ((error = dns_p_push(P, DNS_S_AN, qname, qlen, rr.type, rr.class, 0, ent->host))) goto error;
			}

			break;
		case DNS_T_AAAA:
			af = AF_INET6;

			goto loop;
		case DNS_T_A:
			af = AF_INET;

		loop:
			for (ent = hosts->head; ent; ent = ent->next) {
				if (ent->af != af || 0 != strcasecmp(qname, ent->host)) continue;

				if ((error = dns_p_push(P, DNS_S_AN, qname, qlen, rr.type, rr.class, 0, &ent->addr))) goto error;
			}

			break;
		default:
			break;
	} /* switch() */

	if (!(A = dns_p_copy(dns_p_make(P->end, &error), P))) goto error;

	return A;
toolong:
	error = DNS_EILLEGAL;
error:
	*error_ = error;

	dns_p_free(A);

	return 0;
} /* dns_hosts_query() */

/*
 * R E S O L V . C O N F  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

struct dns_resolv_conf *dns_resconf_open(int *error) {
	static const struct dns_resolv_conf resconf_initializer = {
	    .lookup = "fb",
	    .family = {AF_INET, AF_INET6},
	    .options =
	        {
	            .ndots = 1,
	            .timeout = 5,
	            .attempts = 2,
	            .tcp = DNS_RESCONF_TCP_ENABLE,
	        },
	    .iface = {.ss_family = AF_INET},
	};
	struct dns_resolv_conf *resconf;
	struct sockaddr_in *sin;

	if (!(resconf = malloc(sizeof *resconf))) goto syerr;

	*resconf = resconf_initializer;

	sin = (struct sockaddr_in *)&resconf->nameserver[0];
	sin->sin_family = AF_INET;
	sin->sin_addr.s_addr = INADDR_ANY;
	sin->sin_port = htons(53);
#if defined(SA_LEN)
	sin->sin_len = sizeof *sin;
#endif

	if (0 != gethostname(resconf->search[0], sizeof resconf->search[0])) goto syerr;

	dns_d_anchor(resconf->search[0], sizeof resconf->search[0], resconf->search[0], strlen(resconf->search[0]));
	dns_d_cleave(resconf->search[0], sizeof resconf->search[0], resconf->search[0], strlen(resconf->search[0]));

	/*
	 * XXX: If gethostname() returned a string without any label
	 *      separator, then search[0][0] should be NUL.
	 */

	dns_resconf_acquire(resconf);

	return resconf;
syerr:
	*error = dns_syerr();

	free(resconf);

	return 0;
} /* dns_resconf_open() */

void dns_resconf_close(struct dns_resolv_conf *resconf) {
	if (!resconf || 1 != dns_resconf_release(resconf)) return /* void */;

	free(resconf);
} /* dns_resconf_close() */

dns_refcount_t dns_resconf_acquire(struct dns_resolv_conf *resconf) {
	return dns_atomic_fetch_add(&resconf->_.refcount);
} /* dns_resconf_acquire() */

dns_refcount_t dns_resconf_release(struct dns_resolv_conf *resconf) {
	return dns_atomic_fetch_sub(&resconf->_.refcount);
} /* dns_resconf_release() */

struct dns_resolv_conf *dns_resconf_mortal(struct dns_resolv_conf *resconf) {
	if (resconf) dns_resconf_release(resconf);

	return resconf;
} /* dns_resconf_mortal() */

struct dns_resolv_conf *dns_resconf_local(int *error_) {
	struct dns_resolv_conf *resconf;
	int error;

	if (!(resconf = dns_resconf_open(&error))) goto error;

	if ((error = dns_resconf_loadpath(resconf, "/etc/resolv.conf"))) {
		/*
		 * NOTE: Both the glibc and BIND9 resolvers ignore a missing
		 * /etc/resolv.conf, defaulting to a nameserver of
		 * 127.0.0.1. See also dns_hints_insert_resconf, and the
		 * default initialization of nameserver[0] in
		 * dns_resconf_open.
		 */
		if (error != ENOENT) goto error;
	}

	if ((error = dns_nssconf_loadpath(resconf, "/etc/nsswitch.conf"))) {
		if (error != ENOENT) goto error;
	}

	return resconf;
error:
	*error_ = error;

	dns_resconf_close(resconf);

	return 0;
} /* dns_resconf_local() */

struct dns_resolv_conf *dns_resconf_root(int *error) {
	struct dns_resolv_conf *resconf;

	if ((resconf = dns_resconf_local(error))) resconf->options.recurse = 1;

	return resconf;
} /* dns_resconf_root() */

static time_t dns_resconf_timeout(const struct dns_resolv_conf *resconf) {
	return (time_t)DNS_PP_MIN(INT_MAX, resconf->options.timeout);
} /* dns_resconf_timeout() */

enum dns_resconf_keyword {
	DNS_RESCONF_NAMESERVER,
	DNS_RESCONF_DOMAIN,
	DNS_RESCONF_SEARCH,
	DNS_RESCONF_LOOKUP,
	DNS_RESCONF_FILE,
	DNS_RESCONF_BIND,
	DNS_RESCONF_CACHE,
	DNS_RESCONF_FAMILY,
	DNS_RESCONF_INET4,
	DNS_RESCONF_INET6,
	DNS_RESCONF_OPTIONS,
	DNS_RESCONF_EDNS0,
	DNS_RESCONF_NDOTS,
	DNS_RESCONF_TIMEOUT,
	DNS_RESCONF_ATTEMPTS,
	DNS_RESCONF_ROTATE,
	DNS_RESCONF_RECURSE,
	DNS_RESCONF_SMART,
	DNS_RESCONF_TCP,
	DNS_RESCONF_TCPx,
	DNS_RESCONF_INTERFACE,
	DNS_RESCONF_ZERO,
	DNS_RESCONF_ONE,
	DNS_RESCONF_ENABLE,
	DNS_RESCONF_ONLY,
	DNS_RESCONF_DISABLE,
}; /* enum dns_resconf_keyword */

static enum dns_resconf_keyword dns_resconf_keyword(const char *word) {
	static const char *words[] = {
	    [DNS_RESCONF_NAMESERVER] = "nameserver",
	    [DNS_RESCONF_DOMAIN] = "domain",
	    [DNS_RESCONF_SEARCH] = "search",
	    [DNS_RESCONF_LOOKUP] = "lookup",
	    [DNS_RESCONF_FILE] = "file",
	    [DNS_RESCONF_BIND] = "bind",
	    [DNS_RESCONF_CACHE] = "cache",
	    [DNS_RESCONF_FAMILY] = "family",
	    [DNS_RESCONF_INET4] = "inet4",
	    [DNS_RESCONF_INET6] = "inet6",
	    [DNS_RESCONF_OPTIONS] = "options",
	    [DNS_RESCONF_EDNS0] = "edns0",
	    [DNS_RESCONF_ROTATE] = "rotate",
	    [DNS_RESCONF_RECURSE] = "recurse",
	    [DNS_RESCONF_SMART] = "smart",
	    [DNS_RESCONF_TCP] = "tcp",
	    [DNS_RESCONF_INTERFACE] = "interface",
	    [DNS_RESCONF_ZERO] = "0",
	    [DNS_RESCONF_ONE] = "1",
	    [DNS_RESCONF_ENABLE] = "enable",
	    [DNS_RESCONF_ONLY] = "only",
	    [DNS_RESCONF_DISABLE] = "disable",
	};
	unsigned i;

	for (i = 0; i < lengthof(words); i++) {
		if (words[i] && 0 == strcasecmp(words[i], word)) return i;
	}

	if (0 == strncasecmp(word, "ndots:", sizeof "ndots:" - 1)) return DNS_RESCONF_NDOTS;

	if (0 == strncasecmp(word, "timeout:", sizeof "timeout:" - 1)) return DNS_RESCONF_TIMEOUT;

	if (0 == strncasecmp(word, "attempts:", sizeof "attempts:" - 1)) return DNS_RESCONF_ATTEMPTS;

	if (0 == strncasecmp(word, "tcp:", sizeof "tcp:" - 1)) return DNS_RESCONF_TCPx;

	return -1;
} /* dns_resconf_keyword() */

/** OpenBSD-style "[1.2.3.4]:53" nameserver syntax */
int dns_resconf_pton(struct sockaddr_storage *ss, const char *src) {
	struct {
		char buf[128], *p;
	} addr = {"", addr.buf};
	unsigned short port = 0;
	struct addrinfo *ai;
	int ch, af = AF_INET;

	while ((ch = *src++)) {
		switch (ch) {
			case ' ':
				/* FALL THROUGH */
			case '\t':
				break;
			case '[':
				break;
			case ']':
				while ((ch = *src++)) {
					if (dns_isdigit(ch)) {
						port *= 10;
						port += ch - '0';
					}
				}

				goto inet;
			case ':':
				af = AF_INET6;

				/* FALL THROUGH */
			default:
				if (addr.p < endof(addr.buf) - 1) *addr.p++ = ch;

				break;
		} /* switch() */
	}     /* while() */
inet:

	port = (!port) ? 53 : port;
	ai = bctbx_ip_address_to_addrinfo(af, SOCK_DGRAM, addr.buf, port);
	if (ai == NULL) return dns_soerr();
	memcpy(ss, ai->ai_addr, ai->ai_addrlen);
	bctbx_freeaddrinfo(ai);
	return 0;
} /* dns_resconf_pton() */

#define dns_resconf_issep(ch) (dns_isspace(ch) || (ch) == ',')
#define dns_resconf_iscom(ch) ((ch) == '#' || (ch) == ';')

int dns_resconf_loadfile(struct dns_resolv_conf *resconf, FILE *fp) {
	unsigned sa_count = 0;
	char words[6][DNS_D_MAXNAME + 1];
	unsigned wp, wc, i, j, n;
	int ch, error;

	rewind(fp);

	do {
		memset(words, '\0', sizeof words);
		wp = 0;
		wc = 0;

		while (EOF != (ch = getc(fp)) && ch != '\n') {
			if (dns_resconf_issep(ch)) {
				if (wp > 0) {
					wp = 0;

					if (++wc >= lengthof(words)) goto skip;
				}
			} else if (dns_resconf_iscom(ch)) {
			skip:
				do {
					ch = getc(fp);
				} while (ch != EOF && ch != '\n');

				break;
			} else if (wp < sizeof words[wc] - 1) {
				words[wc][wp++] = ch;
			} else {
				wp = 0; /* drop word */
				goto skip;
			}
		}

		if (wp > 0) wc++;

		if (wc < 2) continue;

		switch (dns_resconf_keyword(words[0])) {
			case DNS_RESCONF_NAMESERVER:
				if (sa_count >= lengthof(resconf->nameserver)) continue;

				if ((error = dns_resconf_pton(&resconf->nameserver[sa_count], words[1]))) continue;

				sa_count++;

				break;
			case DNS_RESCONF_DOMAIN:
			case DNS_RESCONF_SEARCH:
				memset(resconf->search, '\0', sizeof resconf->search);

				for (i = 1, j = 0; i < wc && j < lengthof(resconf->search); i++, j++)
					dns_d_anchor(resconf->search[j], sizeof resconf->search[j], words[i], strlen(words[i]));

				break;
			case DNS_RESCONF_LOOKUP:
				for (i = 1, j = 0; i < wc && j < lengthof(resconf->lookup); i++) {
					switch (dns_resconf_keyword(words[i])) {
						case DNS_RESCONF_FILE:
							resconf->lookup[j++] = 'f';

							break;
						case DNS_RESCONF_BIND:
							resconf->lookup[j++] = 'b';

							break;
						case DNS_RESCONF_CACHE:
							resconf->lookup[j++] = 'c';

							break;
						default:
							break;
					} /* switch() */
				}     /* for() */

				break;
			case DNS_RESCONF_FAMILY:
				for (i = 1, j = 0; i < wc && j < lengthof(resconf->family); i++) {
					switch (dns_resconf_keyword(words[i])) {
						case DNS_RESCONF_INET4:
							resconf->family[j++] = AF_INET;

							break;
						case DNS_RESCONF_INET6:
							resconf->family[j++] = AF_INET6;

							break;
						default:
							break;
					}
				}

				break;
			case DNS_RESCONF_OPTIONS:
				for (i = 1; i < wc; i++) {
					switch (dns_resconf_keyword(words[i])) {
						case DNS_RESCONF_EDNS0:
							resconf->options.edns0 = 1;

							break;
						case DNS_RESCONF_NDOTS:
							for (j = sizeof "ndots:" - 1, n = 0; dns_isdigit(words[i][j]); j++) {
								n *= 10;
								n += words[i][j] - '0';
							} /* for() */

							resconf->options.ndots = n;

							break;
						case DNS_RESCONF_TIMEOUT:
							for (j = sizeof "timeout:" - 1, n = 0; dns_isdigit(words[i][j]); j++) {
								n *= 10;
								n += words[i][j] - '0';
							} /* for() */

							resconf->options.timeout = n;

							break;
						case DNS_RESCONF_ATTEMPTS:
							for (j = sizeof "attempts:" - 1, n = 0; dns_isdigit(words[i][j]); j++) {
								n *= 10;
								n += words[i][j] - '0';
							} /* for() */

							resconf->options.attempts = n;

							break;
						case DNS_RESCONF_ROTATE:
							resconf->options.rotate = 1;

							break;
						case DNS_RESCONF_RECURSE:
							resconf->options.recurse = 1;

							break;
						case DNS_RESCONF_SMART:
							resconf->options.smart = 1;

							break;
						case DNS_RESCONF_TCP:
							resconf->options.tcp = DNS_RESCONF_TCP_ONLY;

							break;
						case DNS_RESCONF_TCPx:
							switch (dns_resconf_keyword(&words[i][sizeof "tcp:" - 1])) {
								case DNS_RESCONF_ENABLE:
									resconf->options.tcp = DNS_RESCONF_TCP_ENABLE;

									break;
								case DNS_RESCONF_ONE:
								case DNS_RESCONF_ONLY:
									resconf->options.tcp = DNS_RESCONF_TCP_ONLY;

									break;
								case DNS_RESCONF_ZERO:
								case DNS_RESCONF_DISABLE:
									resconf->options.tcp = DNS_RESCONF_TCP_DISABLE;

									break;
								default:
									break;
							} /* switch() */

							break;
						default:
							break;
					} /* switch() */
				}     /* for() */

				break;
			case DNS_RESCONF_INTERFACE:
				for (i = 0, n = 0; dns_isdigit(words[2][i]); i++) {
					n *= 10;
					n += words[2][i] - '0';
				}

				dns_resconf_setiface(resconf, words[1], n);

				break;
			default:
				break;
		} /* switch() */
	} while (ch != EOF);

	return 0;
} /* dns_resconf_loadfile() */

int dns_resconf_loadpath(struct dns_resolv_conf *resconf, const char *path) {
	FILE *fp;
	int error;

	if (!(fp = dns_fopen(path, "rt", &error))) return error;

	error = dns_resconf_loadfile(resconf, fp);

	fclose(fp);

	return error;
} /* dns_resconf_loadpath() */

#ifdef USE_FIXED_NAMESERVERS
int dns_resconf_load_fixed_nameservers(struct dns_resolv_conf *resconf) {
	const char *const nameservers[] = {"8.8.8.8", "8.8.4.4"};
	int i;
	int error = 0;

	for (i = 0; !error && (i < lengthof(nameservers)); i++) {
		error = dns_resconf_pton(&resconf->nameserver[i], nameservers[i]);
	}

	return error;
}
#endif /* USE_FIXED_NAMESERVERS */

#ifdef USE_STRUCT_RES_STATE_NAMESERVERS
int dns_resconf_load_struct_res_state_nameservers(struct dns_resolv_conf *resconf) {
	int i;
	struct __res_state *rs = __res_get_state();

	for (i = 0; i < rs->nscount; i++) {
		memcpy(&resconf->nameserver[i], (struct sockaddr_storage *)&rs->nsaddr_list[i], sizeof(struct sockaddr_in));
	}

	return 0;
}
#endif /* USE_STRUCT_RES_STATE_NAMESERVERS */

#if defined(_WIN32) && !defined(USE_FIXED_NAMESERVERS)
int dns_resconf_loadwin(struct dns_resolv_conf *resconf) {
	FIXED_INFO *pFixedInfo;
	ULONG ulOutBufLen;
	DWORD dwRetVal;
	IP_ADDR_STRING *pIPAddr;
	unsigned sa_count = 0;
	int error;

	pFixedInfo = (FIXED_INFO *)malloc(sizeof(FIXED_INFO));
	if (pFixedInfo == NULL) {
		return -1;
	}
	ulOutBufLen = sizeof(FIXED_INFO);
	if (GetNetworkParams(pFixedInfo, &ulOutBufLen) == ERROR_BUFFER_OVERFLOW) {
		free(pFixedInfo);
		pFixedInfo = (FIXED_INFO *)malloc(ulOutBufLen);
		if (pFixedInfo == NULL) {
			return -1;
		}
	}

	if ((dwRetVal = GetNetworkParams(pFixedInfo, &ulOutBufLen)) == NO_ERROR) {
		memset(resconf->search, '\0', sizeof resconf->search);
		memcpy(resconf->search[0], pFixedInfo->DomainName, sizeof pFixedInfo->DomainName);
		pIPAddr = &pFixedInfo->DnsServerList;
		do {
			error = dns_resconf_pton(&resconf->nameserver[sa_count], pIPAddr->IpAddress.String);
			pIPAddr = pIPAddr->Next;
			sa_count++;
		} while (!error && pIPAddr && (sa_count < lengthof(resconf->nameserver)));
	}
	free(pFixedInfo);
	return 0;
}
#endif /* dns_resconf_loadwin() */

#ifdef __ANDROID__
int dns_resconf_loadandroid(struct dns_resolv_conf *resconf) {
	char dns[PROP_VALUE_MAX];
	char prop_name[PROP_NAME_MAX];
	unsigned int sa_count = 0;
	int error = 0;
	unsigned int i;

	for (i = 1; !error && (i <= lengthof(resconf->nameserver)); i++) {
		snprintf(prop_name, sizeof(prop_name), "net.dns%d", i);
		if (__system_property_get(prop_name, dns) > 0) {
			if (dns_resconf_pton(&resconf->nameserver[sa_count], dns) == 0) {
				sa_count++;
			}
		}
	}

	if (sa_count == 0) {
		/* No net.dnsX property found, return an error. */
		error = -1;
	}

	return error;
} /* dns_resconf_loadandroid */
#endif

#ifdef HAVE_RESINIT

static int guess_scope_id(void) {
	struct ifaddrs *ifp;
	struct ifaddrs *ifpstart;
	int scope_id = -1;

	if (getifaddrs(&ifpstart) < 0) {
		return -1;
	}
#ifndef __linux__
#define UP_FLAG IFF_UP /* interface is up */
#else
#define UP_FLAG IFF_RUNNING /* resources allocated */
#endif

	for (ifp = ifpstart; ifp != NULL; ifp = ifp->ifa_next) {
		if (ifp->ifa_addr && ifp->ifa_addr->sa_family == AF_INET6 && (ifp->ifa_flags & UP_FLAG) &&
		    !(ifp->ifa_flags & IFF_LOOPBACK)) {
			struct sockaddr_in6 *in6 = (struct sockaddr_in6 *)ifp->ifa_addr;
			if (in6->sin6_addr.__u6_addr.__u6_addr16[0] == 0x80fe) {
				scope_id = in6->sin6_scope_id;
				belle_sip_warning("Best guess for scope id is %i", scope_id);
				break;
			}
		}
	}
	freeifaddrs(ifpstart);

	return scope_id;
}

int dns_resconf_loadfromresolv(struct dns_resolv_conf *resconf) {
	struct __res_state res;
	union res_sockaddr_union addresses[3];
	int i, error, write_index;

	if ((error = res_ninit(&res))) {
		return error;
	}

	error = res_getservers(&res, addresses, 3);
	if (error > 0) {
		for (i = 0, write_index = 0; i < error; i++) {

			if ((addresses[i].sin.sin_family == AF_INET6) &&
			    (addresses[i].sin6.sin6_addr.__u6_addr.__u6_addr16[0] == 0x80fe) /*local link*/
			    && (addresses[i].sin6.sin6_scope_id == 0)) {
				char ip[32];
				int scope_id;
				bctbx_sockaddr_to_printable_ip_address((struct sockaddr *)&addresses[i].sin6, sizeof(struct sockaddr),
				                                       ip, sizeof(ip));
				belle_sip_warning("DNS entry [%s] has no scope id, will try to guess it.", ip);
				scope_id = guess_scope_id();
				if (scope_id == 0) {
					belle_sip_error("Could not guess the scope id, dns server [%s] cannot be used.", ip);
				} else {
					addresses[i].sin6.sin6_scope_id = scope_id;
					memcpy(&resconf->nameserver[write_index++], &addresses[i], sizeof(union res_sockaddr_union));
				}
			} else {
				memcpy(&resconf->nameserver[write_index++], &addresses[i], sizeof(union res_sockaddr_union));
			}
		}
		error = 0;
	} else error = -1;
	res_ndestroy(&res);
	return error;
}
#endif /*HAVE_RESINIT*/

struct dns_anyconf {
	char *token[16];
	unsigned count;
	char buffer[1024], *tp, *cp;
}; /* struct dns_anyconf */

static void dns_anyconf_reset(struct dns_anyconf *cf) {
	cf->count = 0;
	cf->tp = cf->cp = cf->buffer;
} /* dns_anyconf_reset() */

static int dns_anyconf_push(struct dns_anyconf *cf) {
	if (!(cf->cp < endof(cf->buffer) && cf->count < lengthof(cf->token))) return ENOMEM;

	*cf->cp++ = '\0';
	cf->token[cf->count++] = cf->tp;
	cf->tp = cf->cp;

	return 0;
} /* dns_anyconf_push() */

static void dns_anyconf_pop(struct dns_anyconf *cf) {
	if (cf->count > 0) {
		--cf->count;
		cf->tp = cf->cp = cf->token[cf->count];
		cf->token[cf->count] = 0;
	}
} /* dns_anyconf_pop() */

static int dns_anyconf_addc(struct dns_anyconf *cf, int ch) {
	if (!(cf->cp < endof(cf->buffer))) return ENOMEM;

	*cf->cp++ = ch;

	return 0;
} /* dns_anyconf_addc() */

static _Bool dns_anyconf_match(const char *pat, int mc) {
	_Bool match;
	int pc;

	if (*pat == '^') {
		match = 0;
		++pat;
	} else {
		match = 1;
	}

	while ((pc = *(const unsigned char *)pat++)) {
		switch (pc) {
			case '%':
				if (!(pc = *(const unsigned char *)pat++)) return !match;

				switch (pc) {
					case 'a':
						if (dns_isalpha(mc)) return match;
						break;
					case 'd':
						if (dns_isdigit(mc)) return match;
						break;
					case 'w':
						if (dns_isalnum(mc)) return match;
						break;
					case 's':
						if (dns_isspace(mc)) return match;
						break;
					default:
						if (mc == pc) return match;
						break;
				} /* switch() */

				break;
			default:
				if (mc == pc) return match;
				break;
		} /* switch() */
	}     /* while() */

	return !match;
} /* dns_anyconf_match() */

static int dns_anyconf_peek(FILE *fp) {
	int ch;
	ch = getc(fp);
	ungetc(ch, fp);
	return ch;
} /* dns_anyconf_peek() */

static size_t dns_anyconf_skip(const char *pat, FILE *fp) {
	size_t count = 0;
	int ch;

	while (EOF != (ch = getc(fp))) {
		if (dns_anyconf_match(pat, ch)) {
			count++;
			continue;
		}

		ungetc(ch, fp);

		break;
	}

	return count;
} /* dns_anyconf_skip() */

static size_t dns_anyconf_scan(struct dns_anyconf *cf, const char *pat, FILE *fp, int *error) {
	size_t len;
	int ch;

	while (EOF != (ch = getc(fp))) {
		if (dns_anyconf_match(pat, ch)) {
			if ((*error = dns_anyconf_addc(cf, ch))) return 0;

			continue;
		} else {
			ungetc(ch, fp);

			break;
		}
	}

	if ((len = cf->cp - cf->tp)) {
		if ((*error = dns_anyconf_push(cf))) return 0;

		return len;
	} else {
		*error = 0;

		return 0;
	}
} /* dns_anyconf_scan() */

DNS_NOTUSED static void dns_anyconf_dump(struct dns_anyconf *cf, FILE *fp) {
	unsigned i;

	fprintf(fp, "tokens:");

	for (i = 0; i < cf->count; i++) {
		fprintf(fp, " %s", cf->token[i]);
	}

	fputc('\n', fp);
} /* dns_anyconf_dump() */

enum dns_nssconf_keyword {
	DNS_NSSCONF_INVALID = 0,
	DNS_NSSCONF_HOSTS = 1,
	DNS_NSSCONF_SUCCESS,
	DNS_NSSCONF_NOTFOUND,
	DNS_NSSCONF_UNAVAIL,
	DNS_NSSCONF_TRYAGAIN,
	DNS_NSSCONF_CONTINUE,
	DNS_NSSCONF_RETURN,
	DNS_NSSCONF_FILES,
	DNS_NSSCONF_DNS,
	DNS_NSSCONF_MDNS,

	DNS_NSSCONF_LAST,
}; /* enum dns_nssconf_keyword */

static enum dns_nssconf_keyword dns_nssconf_keyword(const char *word) {
	static const char *list[] = {
	    [DNS_NSSCONF_HOSTS] = "hosts",     [DNS_NSSCONF_SUCCESS] = "success",   [DNS_NSSCONF_NOTFOUND] = "notfound",
	    [DNS_NSSCONF_UNAVAIL] = "unavail", [DNS_NSSCONF_TRYAGAIN] = "tryagain", [DNS_NSSCONF_CONTINUE] = "continue",
	    [DNS_NSSCONF_RETURN] = "return",   [DNS_NSSCONF_FILES] = "files",       [DNS_NSSCONF_DNS] = "dns",
	    [DNS_NSSCONF_MDNS] = "mdns",
	};
	unsigned i;

	for (i = 1; i < lengthof(list); i++) {
		if (list[i] && 0 == strcasecmp(list[i], word)) return i;
	}

	return DNS_NSSCONF_INVALID;
} /* dns_nssconf_keyword() */

static enum dns_nssconf_keyword dns_nssconf_c2k(int ch) {
	static const char map[] = {
	    ['S'] = DNS_NSSCONF_SUCCESS,  ['N'] = DNS_NSSCONF_NOTFOUND, ['U'] = DNS_NSSCONF_UNAVAIL,
	    ['T'] = DNS_NSSCONF_TRYAGAIN, ['C'] = DNS_NSSCONF_CONTINUE, ['R'] = DNS_NSSCONF_RETURN,
	    ['f'] = DNS_NSSCONF_FILES,    ['F'] = DNS_NSSCONF_FILES,    ['d'] = DNS_NSSCONF_DNS,
	    ['D'] = DNS_NSSCONF_DNS,      ['b'] = DNS_NSSCONF_DNS,      ['B'] = DNS_NSSCONF_DNS,
	    ['m'] = DNS_NSSCONF_MDNS,     ['M'] = DNS_NSSCONF_MDNS,
	};

	return (ch >= 0 && ch < (int)lengthof(map)) ? map[ch] : DNS_NSSCONF_INVALID;
} /* dns_nssconf_c2k() */

DNS_PRAGMA_PUSH
DNS_PRAGMA_QUIET

static int dns_nssconf_k2c(int k) {
	static const char map[DNS_NSSCONF_LAST] = {
	    [DNS_NSSCONF_SUCCESS] = 'S',  [DNS_NSSCONF_NOTFOUND] = 'N', [DNS_NSSCONF_UNAVAIL] = 'U',
	    [DNS_NSSCONF_TRYAGAIN] = 'T', [DNS_NSSCONF_CONTINUE] = 'C', [DNS_NSSCONF_RETURN] = 'R',
	    [DNS_NSSCONF_FILES] = 'f',    [DNS_NSSCONF_DNS] = 'b',      [DNS_NSSCONF_MDNS] = 'm',
	};

	return (k >= 0 && k < (int)lengthof(map)) ? (map[k] ? map[k] : '?') : '?';
} /* dns_nssconf_k2c() */

static const char *dns_nssconf_k2s(int k) {
	static const char *const map[DNS_NSSCONF_LAST] = {
	    [DNS_NSSCONF_SUCCESS] = "SUCCESS",   [DNS_NSSCONF_NOTFOUND] = "NOTFOUND", [DNS_NSSCONF_UNAVAIL] = "UNAVAIL",
	    [DNS_NSSCONF_TRYAGAIN] = "TRYAGAIN", [DNS_NSSCONF_CONTINUE] = "continue", [DNS_NSSCONF_RETURN] = "return",
	    [DNS_NSSCONF_FILES] = "files",       [DNS_NSSCONF_DNS] = "dns",           [DNS_NSSCONF_MDNS] = "mdns",
	};

	return (k >= 0 && k < (int)lengthof(map)) ? (map[k] ? map[k] : "") : "";
} /* dns_nssconf_k2s() */

DNS_PRAGMA_POP

int dns_nssconf_loadfile(struct dns_resolv_conf *resconf, FILE *fp) {
	enum dns_nssconf_keyword source, status, action;
	char lookup[sizeof resconf->lookup] = "", *lp;
	struct dns_anyconf cf;
	size_t i;
	int error;

	while (!feof(fp) && !ferror(fp)) {
		dns_anyconf_reset(&cf);

		dns_anyconf_skip("%s", fp);

		if (!dns_anyconf_scan(&cf, "%w_", fp, &error)) goto nextent;

		if (DNS_NSSCONF_HOSTS != dns_nssconf_keyword(cf.token[0])) goto nextent;

		dns_anyconf_pop(&cf);

		if (!dns_anyconf_skip(": \t", fp)) goto nextent;

		*(lp = lookup) = '\0';

		while (dns_anyconf_scan(&cf, "%w_", fp, &error)) {
			dns_anyconf_skip(" \t", fp);

			if ('[' == dns_anyconf_peek(fp)) {
				dns_anyconf_skip("[ \t", fp);

				while (dns_anyconf_scan(&cf, "%w_!", fp, &error)) {
					dns_anyconf_skip("= \t", fp);
					if (!dns_anyconf_scan(&cf, "%w_", fp, &error)) {
						dns_anyconf_pop(&cf);           /* discard status */
						dns_anyconf_skip("^#;]\n", fp); /* skip to end of criteria */
						break;
					}
					dns_anyconf_skip(" \t", fp);
				}

				dns_anyconf_skip("] \t", fp);
			}

			if ((size_t)(endof(lookup) - lp) < cf.count + 1) /* +1 for '\0' */
				goto nextsrc;

			source = dns_nssconf_keyword(cf.token[0]);

			switch (source) {
				case DNS_NSSCONF_DNS:
				case DNS_NSSCONF_MDNS:
				case DNS_NSSCONF_FILES:
					*lp++ = dns_nssconf_k2c(source);
					break;
				default:
					goto nextsrc;
			}

			for (i = 1; i + 1 < cf.count; i += 2) {
				status = dns_nssconf_keyword(cf.token[i]);
				action = dns_nssconf_keyword(cf.token[i + 1]);

				switch (status) {
					case DNS_NSSCONF_SUCCESS:
					case DNS_NSSCONF_NOTFOUND:
					case DNS_NSSCONF_UNAVAIL:
					case DNS_NSSCONF_TRYAGAIN:
						*lp++ = dns_nssconf_k2c(status);
						break;
					default:
						continue;
				}

				switch (action) {
					case DNS_NSSCONF_CONTINUE:
					case DNS_NSSCONF_RETURN:
						break;
					default:
						action = (status == DNS_NSSCONF_SUCCESS) ? DNS_NSSCONF_RETURN : DNS_NSSCONF_CONTINUE;
						break;
				}

				*lp++ = dns_nssconf_k2c(action);
			}
		nextsrc:
			*lp = '\0';
			dns_anyconf_reset(&cf);
		}
	nextent:
		dns_anyconf_skip("^\n", fp);
	}

	if (*lookup) strncpy(resconf->lookup, lookup, sizeof resconf->lookup);

	return 0;
} /* dns_nssconf_loadfile() */

int dns_nssconf_loadpath(struct dns_resolv_conf *resconf, const char *path) {
	FILE *fp;
	int error;

	if (!(fp = dns_fopen(path, "rt", &error))) return error;

	error = dns_nssconf_loadfile(resconf, fp);

	fclose(fp);

	return error;
} /* dns_nssconf_loadpath() */

struct dns_nssconf_source {
	enum dns_nssconf_keyword source, success, notfound, unavail, tryagain;
}; /* struct dns_nssconf_source */

typedef unsigned dns_nssconf_i;

static DNS_INLINE int dns_nssconf_peek(const struct dns_resolv_conf *resconf, dns_nssconf_i state) {
	return (state < lengthof(resconf->lookup) && resconf->lookup[state]) ? resconf->lookup[state] : 0;
} /* dns_nssconf_peek() */

static _Bool
dns_nssconf_next(struct dns_nssconf_source *src, const struct dns_resolv_conf *resconf, dns_nssconf_i *state) {
	int source, status, action;

	src->source = DNS_NSSCONF_INVALID;
	src->success = DNS_NSSCONF_RETURN;
	src->notfound = DNS_NSSCONF_CONTINUE;
	src->unavail = DNS_NSSCONF_CONTINUE;
	src->tryagain = DNS_NSSCONF_CONTINUE;

	while ((source = dns_nssconf_peek(resconf, *state))) {
		source = dns_nssconf_c2k(source);
		++*state;

		switch (source) {
			case DNS_NSSCONF_FILES:
			case DNS_NSSCONF_DNS:
			case DNS_NSSCONF_MDNS:
				src->source = source;
				break;
			default:
				continue;
		}

		while ((status = dns_nssconf_peek(resconf, *state)) && (action = dns_nssconf_peek(resconf, *state + 1))) {
			status = dns_nssconf_c2k(status);
			action = dns_nssconf_c2k(action);

			switch (action) {
				case DNS_NSSCONF_RETURN:
				case DNS_NSSCONF_CONTINUE:
					break;
				default:
					goto done;
			}

			switch (status) {
				case DNS_NSSCONF_SUCCESS:
					src->success = action;
					break;
				case DNS_NSSCONF_NOTFOUND:
					src->notfound = action;
					break;
				case DNS_NSSCONF_UNAVAIL:
					src->unavail = action;
					break;
				case DNS_NSSCONF_TRYAGAIN:
					src->tryagain = action;
					break;
				default:
					goto done;
			}

			*state += 2;
		}

		break;
	}
done:
	return src->source != DNS_NSSCONF_INVALID;
} /* dns_nssconf_next() */

static int dns_nssconf_dump_status(int status, int action, unsigned *count, FILE *fp) {
	switch (status) {
		case DNS_NSSCONF_SUCCESS:
			if (action == DNS_NSSCONF_RETURN) return 0;
			break;
		default:
			if (action == DNS_NSSCONF_CONTINUE) return 0;
			break;
	}

	fputc(' ', fp);

	if (!*count) fputc('[', fp);

	fprintf(fp, "%s=%s", dns_nssconf_k2s(status), dns_nssconf_k2s(action));

	++*count;

	return 0;
} /* dns_nssconf_dump_status() */

int dns_nssconf_dump(struct dns_resolv_conf *resconf, FILE *fp) {
	struct dns_nssconf_source src;
	dns_nssconf_i i = 0;

	fputs("hosts:", fp);

	while (dns_nssconf_next(&src, resconf, &i)) {
		unsigned n = 0;

		fprintf(fp, " %s", dns_nssconf_k2s(src.source));

		dns_nssconf_dump_status(DNS_NSSCONF_SUCCESS, src.success, &n, fp);
		dns_nssconf_dump_status(DNS_NSSCONF_NOTFOUND, src.notfound, &n, fp);
		dns_nssconf_dump_status(DNS_NSSCONF_UNAVAIL, src.unavail, &n, fp);
		dns_nssconf_dump_status(DNS_NSSCONF_TRYAGAIN, src.tryagain, &n, fp);

		if (n) fputc(']', fp);
	}

	fputc('\n', fp);

	return 0;
} /* dns_nssconf_dump() */

int dns_resconf_setiface(struct dns_resolv_conf *resconf, const char *addr, unsigned short port) {
	int af = (strchr(addr, ':')) ? AF_INET6 : AF_INET;
	int error;

	if ((error = dns_pton(af, addr, dns_sa_addr(af, &resconf->iface, NULL)))) return error;

	*dns_sa_port(af, &resconf->iface) = htons(port);
	resconf->iface.ss_family = af;

	return 0;
} /* dns_resconf_setiface() */

size_t dns_resconf_search(
    void *dst, size_t lim, const void *qname, size_t qlen, struct dns_resolv_conf *resconf, dns_resconf_i_t *state) {
	unsigned srchi = 0xff & (*state >> 8);
	unsigned ndots = 0xff & (*state >> 16);
	unsigned len = 0;
	const char *qp, *qe;

	switch (0xff & *state) {
		case 0:
			qp = qname;
			qe = qp + qlen;

			while ((qp = memchr(qp, '.', qe - qp))) {
				ndots++;
				qp++;
			}

			++*state;

			if (ndots >= resconf->options.ndots) {
				len = dns_d_anchor(dst, lim, qname, qlen);

				break;
			}

			/* FALL THROUGH */
		case 1:
			if (srchi < lengthof(resconf->search) && resconf->search[srchi][0] && strcmp(resconf->search[srchi], ".")) {
				len = dns_d_anchor(dst, lim, qname, qlen);
				len +=
				    dns_strlcpy((char *)dst + DNS_PP_MIN(len, lim), resconf->search[srchi], lim - DNS_PP_MIN(len, lim));

				srchi++;

				break;
			}

			++*state;

			/* FALL THROUGH */
		case 2:
			++*state;

			if (ndots < resconf->options.ndots) {
				len = dns_d_anchor(dst, lim, qname, qlen);

				break;
			}

			/* FALL THROUGH */
		default:
			break;
	} /* switch() */

	*state = ((0xff & *state) << 0) | ((0xff & srchi) << 8) | ((0xff & ndots) << 16);

	if (lim > 0) ((char *)dst)[DNS_PP_MIN(lim - 1, len)] = '\0';

	return len;
} /* dns_resconf_search() */

int dns_resconf_dump(struct dns_resolv_conf *resconf, FILE *fp) {
	unsigned i;
	int af;

	for (i = 0; i < lengthof(resconf->nameserver) && (af = resconf->nameserver[i].ss_family) != AF_UNSPEC; i++) {
		char addr[INET6_ADDRSTRLEN + 1] = "[INVALID]";
		unsigned short port;

		dns_inet_ntop(af, dns_sa_addr(af, &resconf->nameserver[i], NULL), addr, sizeof addr);
		port = ntohs(*dns_sa_port(af, &resconf->nameserver[i]));

		if (port == 53) fprintf(fp, "nameserver %s\n", addr);
		else fprintf(fp, "nameserver [%s]:%hu\n", addr, port);
	}

	fprintf(fp, "search");

	for (i = 0; i < lengthof(resconf->search) && resconf->search[i][0]; i++)
		fprintf(fp, " %s", resconf->search[i]);

	fputc('\n', fp);

	fputs("; ", fp);
	dns_nssconf_dump(resconf, fp);

	fprintf(fp, "lookup");

	for (i = 0; i < lengthof(resconf->lookup) && resconf->lookup[i]; i++) {
		switch (resconf->lookup[i]) {
			case 'b':
				fprintf(fp, " bind");
				break;
			case 'f':
				fprintf(fp, " file");
				break;
			case 'c':
				fprintf(fp, " cache");
				break;
		}
	}

	fputc('\n', fp);

	fprintf(fp, "options ndots:%u timeout:%u attempts:%u", resconf->options.ndots, resconf->options.timeout,
	        resconf->options.attempts);

	if (resconf->options.edns0) fprintf(fp, " edns0");
	if (resconf->options.rotate) fprintf(fp, " rotate");
	if (resconf->options.recurse) fprintf(fp, " recurse");
	if (resconf->options.smart) fprintf(fp, " smart");

	switch (resconf->options.tcp) {
		case DNS_RESCONF_TCP_ENABLE:
			break;
		case DNS_RESCONF_TCP_ONLY:
			fprintf(fp, " tcp");
			break;
		case DNS_RESCONF_TCP_DISABLE:
			fprintf(fp, " tcp:disable");
			break;
	}

	fputc('\n', fp);

	if ((af = resconf->iface.ss_family) != AF_UNSPEC) {
		char addr[INET6_ADDRSTRLEN + 1] = "[INVALID]";

		dns_inet_ntop(af, dns_sa_addr(af, &resconf->iface, NULL), addr, sizeof addr);

		fprintf(fp, "interface %s %hu\n", addr, ntohs(*dns_sa_port(af, &resconf->iface)));
	}

	return 0;
} /* dns_resconf_dump() */

/*
 * H I N T  S E R V E R  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

struct dns_hints_soa {
	unsigned char zone[DNS_D_MAXNAME + 1];

	struct {
		struct sockaddr_storage ss;
		unsigned priority;
	} addrs[16];

	unsigned count;

	struct dns_hints_soa *next;
}; /* struct dns_hints_soa */

struct dns_hints {
	dns_atomic_t refcount;

	struct dns_hints_soa *head;
}; /* struct dns_hints */

struct dns_hints *dns_hints_open(struct dns_resolv_conf *resconf, int *error) {
	static const struct dns_hints H_initializer;
	struct dns_hints *H;

	(void)resconf;

	if (!(H = malloc(sizeof *H))) goto syerr;

	*H = H_initializer;

	dns_hints_acquire(H);

	return H;
syerr:
	*error = dns_syerr();

	free(H);

	return 0;
} /* dns_hints_open() */

void dns_hints_close(struct dns_hints *H) {
	struct dns_hints_soa *soa, *nxt;

	if (!H || 1 != dns_hints_release(H)) return /* void */;

	for (soa = H->head; soa; soa = nxt) {
		nxt = soa->next;

		free(soa);
	}

	free(H);

	return /* void */;
} /* dns_hints_close() */

dns_refcount_t dns_hints_acquire(struct dns_hints *H) {
	return dns_atomic_fetch_add(&H->refcount);
} /* dns_hints_acquire() */

dns_refcount_t dns_hints_release(struct dns_hints *H) {
	return dns_atomic_fetch_sub(&H->refcount);
} /* dns_hints_release() */

struct dns_hints *dns_hints_mortal(struct dns_hints *hints) {
	if (hints) dns_hints_release(hints);

	return hints;
} /* dns_hints_mortal() */

struct dns_hints *dns_hints_local(struct dns_resolv_conf *resconf, int *error_) {
	struct dns_hints *hints = 0;
	int error;

	if (resconf) dns_resconf_acquire(resconf);
	else if (!(resconf = dns_resconf_local(&error))) goto error;

	if (!(hints = dns_hints_open(resconf, &error))) goto error;

	error = 0;

	if (0 == dns_hints_insert_resconf(hints, ".", resconf, &error) && error) goto error;

	dns_resconf_close(resconf);

	return hints;
error:
	*error_ = error;

	dns_resconf_close(resconf);
	dns_hints_close(hints);

	return 0;
} /* dns_hints_local() */

struct dns_hints *dns_hints_root(struct dns_resolv_conf *resconf, int *error_) {
	static const struct {
		int af;
		char addr[INET6_ADDRSTRLEN];
	} root_hints[] = {
	    {AF_INET, "198.41.0.4"},            /* A.ROOT-SERVERS.NET. */
	    {AF_INET6, "2001:503:ba3e::2:30"},  /* A.ROOT-SERVERS.NET. */
	    {AF_INET, "192.228.79.201"},        /* B.ROOT-SERVERS.NET. */
	    {AF_INET6, "2001:500:84::b"},       /* B.ROOT-SERVERS.NET. */
	    {AF_INET, "192.33.4.12"},           /* C.ROOT-SERVERS.NET. */
	    {AF_INET6, "2001:500:2::c"},        /* C.ROOT-SERVERS.NET. */
	    {AF_INET, "199.7.91.13"},           /* D.ROOT-SERVERS.NET. */
	    {AF_INET6, "2001:500:2d::d"},       /* D.ROOT-SERVERS.NET. */
	    {AF_INET, "192.203.230.10"},        /* E.ROOT-SERVERS.NET. */
	    {AF_INET, "192.5.5.241"},           /* F.ROOT-SERVERS.NET. */
	    {AF_INET6, "2001:500:2f::f"},       /* F.ROOT-SERVERS.NET. */
	    {AF_INET, "192.112.36.4"},          /* G.ROOT-SERVERS.NET. */
	    {AF_INET, "128.63.2.53"},           /* H.ROOT-SERVERS.NET. */
	    {AF_INET6, "2001:500:1::803f:235"}, /* H.ROOT-SERVERS.NET. */
	    {AF_INET, "192.36.148.17"},         /* I.ROOT-SERVERS.NET. */
	    {AF_INET6, "2001:7FE::53"},         /* I.ROOT-SERVERS.NET. */
	    {AF_INET, "192.58.128.30"},         /* J.ROOT-SERVERS.NET. */
	    {AF_INET6, "2001:503:c27::2:30"},   /* J.ROOT-SERVERS.NET. */
	    {AF_INET, "193.0.14.129"},          /* K.ROOT-SERVERS.NET. */
	    {AF_INET6, "2001:7FD::1"},          /* K.ROOT-SERVERS.NET. */
	    {AF_INET, "199.7.83.42"},           /* L.ROOT-SERVERS.NET. */
	    {AF_INET6, "2001:500:3::42"},       /* L.ROOT-SERVERS.NET. */
	    {AF_INET, "202.12.27.33"},          /* M.ROOT-SERVERS.NET. */
	    {AF_INET6, "2001:DC3::35"},         /* M.ROOT-SERVERS.NET. */
	};
	struct dns_hints *hints = 0;
	struct sockaddr_storage ss;
	unsigned i;
	int error, af;

	if (!(hints = dns_hints_open(resconf, &error))) goto error;

	for (i = 0; i < lengthof(root_hints); i++) {
		af = root_hints[i].af;

		if ((error = dns_pton(af, root_hints[i].addr, dns_sa_addr(af, &ss, NULL)))) goto error;

		*dns_sa_port(af, &ss) = htons(53);
		ss.ss_family = af;

		if ((error = dns_hints_insert(hints, ".", (struct sockaddr *)&ss, 1))) goto error;
	}

	return hints;
error:
	*error_ = error;

	dns_hints_close(hints);

	return 0;
} /* dns_hints_root() */

static struct dns_hints_soa *dns_hints_fetch(struct dns_hints *H, const char *zone) {
	struct dns_hints_soa *soa;

	for (soa = H->head; soa; soa = soa->next) {
		if (0 == strcasecmp(zone, (char *)soa->zone)) return soa;
	}

	return 0;
} /* dns_hints_fetch() */

int dns_hints_insert(struct dns_hints *H, const char *zone, const struct sockaddr *sa, unsigned priority) {
	static const struct dns_hints_soa soa_initializer;
	struct dns_hints_soa *soa;
	unsigned i;

	if (!(soa = dns_hints_fetch(H, zone))) {
		if (!(soa = malloc(sizeof *soa))) return dns_syerr();
		*soa = soa_initializer;
		dns_strlcpy((char *)soa->zone, zone, sizeof soa->zone);

		soa->next = H->head;
		H->head = soa;
	}

	i = soa->count % lengthof(soa->addrs);

	memcpy(&soa->addrs[i].ss, sa, dns_sa_len(sa));

	soa->addrs[i].priority = DNS_PP_MAX(1, priority);

	if (soa->count < lengthof(soa->addrs)) soa->count++;

	return 0;
} /* dns_hints_insert() */

static _Bool dns_hints_isinaddr_any(const void *sa) {
	struct in_addr *addr;

	if (dns_sa_family(sa) != AF_INET) return 0;

	addr = dns_sa_addr(AF_INET, sa, NULL);
	return addr->s_addr == htonl(INADDR_ANY);
}

unsigned
dns_hints_insert_resconf(struct dns_hints *H, const char *zone, const struct dns_resolv_conf *resconf, int *error_) {
	unsigned i, n, p;
	int error;

	for (i = 0, n = 0, p = 1; i < lengthof(resconf->nameserver) && resconf->nameserver[i].ss_family != AF_UNSPEC;
	     i++, n++) {
		union {
			struct sockaddr_in sin;
		} tmp;
		struct sockaddr *ns;

		/*
		 * dns_resconf_open initializes nameserver[0] to INADDR_ANY.
		 *
		 * Traditionally the semantics of 0.0.0.0 meant the default
		 * interface, which evolved to mean the loopback interface.
		 * See comment block preceding resolv/res_init.c:res_init in
		 * glibc 2.23. As of 2.23, glibc no longer translates
		 * 0.0.0.0 despite the code comment, but it does default to
		 * 127.0.0.1 when no nameservers are present.
		 *
		 * BIND9 as of 9.10.3 still translates 0.0.0.0 to 127.0.0.1.
		 * See lib/lwres/lwconfig.c:lwres_create_addr and the
		 * convert_zero flag. 127.0.0.1 is also the default when no
		 * nameservers are present.
		 */
		if (dns_hints_isinaddr_any(&resconf->nameserver[i])) {
			memcpy(&tmp.sin, &resconf->nameserver[i], sizeof tmp.sin);
			tmp.sin.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
			ns = (struct sockaddr *)&tmp.sin;
		} else {
			ns = (struct sockaddr *)&resconf->nameserver[i];
		}

		if ((error = dns_hints_insert(H, zone, ns, p))) goto error;

		p += !resconf->options.rotate;
	}

	return n;
error:
	*error_ = error;

	return n;
} /* dns_hints_insert_resconf() */

static int dns_hints_i_cmp(unsigned a, unsigned b, struct dns_hints_i *i, struct dns_hints_soa *soa) {
	int cmp;

	if ((cmp = soa->addrs[a].priority - soa->addrs[b].priority)) return cmp;

	return dns_k_shuffle16(a, i->state.seed) - dns_k_shuffle16(b, i->state.seed);
} /* dns_hints_i_cmp() */

static unsigned dns_hints_i_start(struct dns_hints_i *i, struct dns_hints_soa *soa) {
	unsigned p0, p;

	p0 = 0;

	for (p = 1; p < soa->count; p++) {
		if (dns_hints_i_cmp(p, p0, i, soa) < 0) p0 = p;
	}

	return p0;
} /* dns_hints_i_start() */

static unsigned dns_hints_i_skip(unsigned p0, struct dns_hints_i *i, struct dns_hints_soa *soa) {
	unsigned pZ, p;

	for (pZ = 0; pZ < soa->count; pZ++) {
		if (dns_hints_i_cmp(pZ, p0, i, soa) > 0) goto cont;
	}

	return soa->count;
cont:
	for (p = pZ + 1; p < soa->count; p++) {
		if (dns_hints_i_cmp(p, p0, i, soa) <= 0) continue;

		if (dns_hints_i_cmp(p, pZ, i, soa) >= 0) continue;

		pZ = p;
	}

	return pZ;
} /* dns_hints_i_skip() */

static struct dns_hints_i *dns_hints_i_init(struct dns_hints_i *i, struct dns_hints *hints) {
	static const struct dns_hints_i i_initializer;
	struct dns_hints_soa *soa;

	i->state = i_initializer.state;

	do {
		i->state.seed = dns_random();
	} while (0 == i->state.seed);

	if ((soa = dns_hints_fetch(hints, i->zone))) {
		i->state.next = dns_hints_i_start(i, soa);
	}

	return i;
} /* dns_hints_i_init() */

unsigned
dns_hints_grep(struct sockaddr **sa, socklen_t *sa_len, unsigned lim, struct dns_hints_i *i, struct dns_hints *H) {
	struct dns_hints_soa *soa;
	unsigned n;

	if (!(soa = dns_hints_fetch(H, i->zone))) return 0;

	n = 0;

	while (i->state.next < soa->count && n < lim) {
		*sa = (struct sockaddr *)&soa->addrs[i->state.next].ss;
		*sa_len = dns_sa_len(*sa);

		sa++;
		sa_len++;
		n++;

		i->state.next = dns_hints_i_skip(i->state.next, i, soa);
	}

	return n;
} /* dns_hints_grep() */

struct dns_packet *dns_hints_query(struct dns_hints *hints, struct dns_packet *Q, int *error_) {
	struct dns_packet *A, *P;
	struct dns_rr rr;
	char zone[DNS_D_MAXNAME + 1];
	size_t zlen;
	struct dns_hints_i i;
	struct sockaddr *sa;
	socklen_t slen;
	int error;

	if (!dns_rr_grep(&rr, 1, dns_rr_i_new(Q, .section = DNS_S_QUESTION), Q, &error)) goto error;

	if (!(zlen = dns_d_expand(zone, sizeof zone, rr.dn.p, Q, &error))) goto error;
	else if (zlen >= sizeof zone) goto toolong;

	P = dns_p_new(512);
	dns_header(P)->qr = 1;

	if ((error = dns_rr_copy(P, &rr, Q))) goto error;

	if ((error = dns_p_push(P, DNS_S_AUTHORITY, ".", strlen("."), DNS_T_NS, DNS_C_IN, 0, "hints.local."))) goto error;

	do {
		i.zone = zone;

		dns_hints_i_init(&i, hints);

		while (dns_hints_grep(&sa, &slen, 1, &i, hints)) {
			int af = sa->sa_family;
			int rtype = (af == AF_INET6) ? DNS_T_AAAA : DNS_T_A;

			if ((error = dns_p_push(P, DNS_S_ADDITIONAL, "hints.local.", strlen("hints.local."), rtype, DNS_C_IN, 0,
			                        dns_sa_addr(af, sa, NULL))))
				goto error;
		}
	} while ((zlen = dns_d_cleave(zone, sizeof zone, zone, zlen)));

	if (!(A = dns_p_copy(dns_p_make(P->end, &error), P))) goto error;

	return A;
toolong:
	error = DNS_EILLEGAL;
error:
	*error_ = error;

	return 0;
} /* dns_hints_query() */

/**
 * Fill a whole sockaddr from the the nameservers' sockaddr contained in the hints. This is needed for scope link IPv6
 *nameservers.
 **/
static void dns_fill_sockaddr_from_hints(struct dns_hints *hints, int af, struct sockaddr *addr) {
	struct dns_hints_soa *soa;
	unsigned i;

	for (soa = hints->head; soa; soa = soa->next) {
		for (i = 0; i < soa->count; i++) {
			if (af != soa->addrs[i].ss.ss_family) continue;

			if ((af == AF_INET) && (memcmp(&((struct sockaddr_in *)&soa->addrs[i].ss)->sin_addr,
			                               &((struct sockaddr_in *)addr)->sin_addr, sizeof(struct in_addr))))
				continue;

			if ((af == AF_INET6) && (memcmp(&((struct sockaddr_in6 *)&soa->addrs[i].ss)->sin6_addr,
			                                &((struct sockaddr_in6 *)addr)->sin6_addr, sizeof(struct in6_addr))))
				continue;

			memcpy(addr, &soa->addrs[i].ss, dns_af_len(af));
			return;
		}
	}
}

int dns_hints_dump(struct dns_hints *hints, FILE *fp) {
	struct dns_hints_soa *soa;
	char addr[INET6_ADDRSTRLEN];
	unsigned i;
	int af, error;

	for (soa = hints->head; soa; soa = soa->next) {
		fprintf(fp, "ZONE \"%s\"\n", soa->zone);

		for (i = 0; i < soa->count; i++) {
			af = soa->addrs[i].ss.ss_family;

			if ((error = dns_ntop(af, dns_sa_addr(af, &soa->addrs[i].ss, NULL), addr, sizeof addr))) return error;

			fprintf(fp, "\t(%d) [%s]:%hu\n", (int)soa->addrs[i].priority, addr,
			        ntohs(*dns_sa_port(af, &soa->addrs[i].ss)));
		}
	}

	return 0;
} /* dns_hints_dump() */

/*
 * C A C H E  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

static dns_refcount_t dns_cache_acquire(struct dns_cache *cache) {
	return dns_atomic_fetch_add(&cache->_.refcount);
} /* dns_cache_acquire() */

static dns_refcount_t dns_cache_release(struct dns_cache *cache) {
	return dns_atomic_fetch_sub(&cache->_.refcount);
} /* dns_cache_release() */

static struct dns_packet *dns_cache_query(struct dns_packet *query, struct dns_cache *cache, int *error) {
	(void)query;
	(void)cache;
	(void)error;

	return NULL;
} /* dns_cache_query() */

static int dns_cache_submit(struct dns_packet *query, struct dns_cache *cache) {
	(void)query;
	(void)cache;

	return 0;
} /* dns_cache_submit() */

static int dns_cache_check(struct dns_cache *cache) {
	(void)cache;

	return 0;
} /* dns_cache_check() */

static struct dns_packet *dns_cache_fetch(struct dns_cache *cache, int *error) {
	(void)cache;
	(void)error;

	return NULL;
} /* dns_cache_fetch() */

static int dns_cache_pollfd(struct dns_cache *cache) {
	(void)cache;

	return -1;
} /* dns_cache_pollfd() */

static short dns_cache_events(struct dns_cache *cache) {
	(void)cache;

	return 0;
} /* dns_cache_events() */

static void dns_cache_clear(struct dns_cache *cache) {
	(void)cache;

	return;
} /* dns_cache_clear() */

struct dns_cache *dns_cache_init(struct dns_cache *cache) {
	static const struct dns_cache c_init = {
	    .acquire = &dns_cache_acquire,
	    .release = &dns_cache_release,
	    .query = &dns_cache_query,
	    .submit = &dns_cache_submit,
	    .check = &dns_cache_check,
	    .fetch = &dns_cache_fetch,
	    .pollfd = &dns_cache_pollfd,
	    .events = &dns_cache_events,
	    .clear = &dns_cache_clear,
	    ._ =
	        {
	            .refcount = 1,
	        },
	};

	*cache = c_init;

	return cache;
} /* dns_cache_init() */

void dns_cache_close(struct dns_cache *cache) {
	if (cache) cache->release(cache);
} /* dns_cache_close() */

/*
 * S O C K E T  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

static void dns_socketclose(int *fd, const struct dns_options *opts) {
	if (opts && opts->closefd.cb) opts->closefd.cb(fd, opts->closefd.arg);

	if (*fd != -1) {
#if _WIN32
		closesocket(*fd);
#else
		close(*fd);
#endif
		*fd = -1;
	}
} /* dns_socketclose() */

#ifndef HAVE_IOCTLSOCKET
#define HAVE_IOCTLSOCKET (_WIN32 || _WIN64)
#endif

#ifndef HAVE_SOCK_CLOEXEC
#if (defined SOCK_CLOEXEC)
#define HAVE_SOCK_CLOEXEC 1
#endif
#endif

#ifndef HAVE_SOCK_NONBLOCK
#if (defined SOCK_NONBLOCK)
#define HAVE_SOCK_NONBLOCK 1
#endif
#endif

#define DNS_SO_MAXTRY 7

static int dns_socket(struct sockaddr *local, int type, int *error_) {
	int fd = -1, flags, error;
#if defined FIONBIO
	unsigned long opt;
#endif

	flags = 0;
#if HAVE_SOCK_CLOEXEC
	flags |= SOCK_CLOEXEC;
#endif
#if HAVE_SOCK_NONBLOCK
	flags |= SOCK_NONBLOCK;
#endif
	if (-1 == (fd = socket(local->sa_family, type | flags, 0))) goto soerr;

	if (local->sa_family == AF_INET6) {
		int value = 0;
		setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, (const char *)&value, sizeof(value));
	}

#if defined F_SETFD && !HAVE_SOCK_CLOEXEC
	if (-1 == fcntl(fd, F_SETFD, 1)) goto syerr;
#endif

#if defined O_NONBLOCK && !HAVE_SOCK_NONBLOCK
	if (-1 == (flags = fcntl(fd, F_GETFL))) goto syerr;
	if (-1 == fcntl(fd, F_SETFL, flags | O_NONBLOCK)) goto syerr;
#elif defined FIONBIO && HAVE_IOCTLSOCKET
	opt = 1;
	if (0 != ioctlsocket(fd, FIONBIO, &opt)) goto soerr;
#endif

#if defined SO_NOSIGPIPE
	if (type != SOCK_DGRAM) {
		if (0 != setsockopt(fd, SOL_SOCKET, SO_NOSIGPIPE, &(int){1}, sizeof(int))) goto soerr;
	}
#endif

	if (local->sa_family != AF_INET && local->sa_family != AF_INET6) return fd;

	if (type != SOCK_DGRAM) return fd;

	/*
	 * FreeBSD, Linux, OpenBSD, OS X, and Solaris use random ports by
	 * default. Though the ephemeral range is quite small on OS X
	 * (49152-65535 on 10.10) and Linux (32768-60999 on 4.4.0, Ubuntu
	 * Xenial). See also RFC 6056.
	 *
	 * TODO: Optionally rely on the kernel to select a random port.
	 */
	if (*dns_sa_port(local->sa_family, local) == 0) {
		/*bellesip: let the system find a random port*/
		return fd;
		/* NB: continue to next bind statement */
	}

	if (0 == bind(fd, local, dns_sa_len(local))) return fd;

	/* FALL THROUGH */
soerr:
	error = dns_soerr();

	goto error;
#if (defined F_SETFD && !HAVE_SOCK_CLOEXEC) || (defined O_NONBLOCK && !HAVE_SOCK_NONBLOCK)
syerr:
	error = dns_syerr();

	goto error;
#endif
error:
	*error_ = error;

	dns_socketclose(&fd, NULL);

	return -1;
} /* dns_socket() */

enum {
	DNS_SO_UDP_INIT = 1,
	DNS_SO_UDP_CONN,
	DNS_SO_UDP_SEND,
	DNS_SO_UDP_RECV,
	DNS_SO_UDP_DONE,

	DNS_SO_TCP_INIT,
	DNS_SO_TCP_CONN,
	DNS_SO_TCP_SEND,
	DNS_SO_TCP_RECV,
	DNS_SO_TCP_DONE,
};

struct dns_socket {
	struct dns_options opts;

	int udp;
	int tcp;

	int *old;
	unsigned onum, olim;

	int type;

	struct sockaddr_storage local, remote;

	struct dns_k_permutor qids;

	struct dns_stat stat;

	/*
	 * NOTE: dns_so_reset() zeroes everything from here down.
	 */
	int state;

	unsigned short qid;
	char qname[DNS_D_MAXNAME + 1];
	size_t qlen;
	enum dns_type qtype;
	enum dns_class qclass;

	struct dns_packet *query;
	size_t qout;

	struct dns_clock elapsed;

	struct dns_packet *answer;
	size_t alen, apos;
	int ip_differ; /*set when remote address and response from which it is received are different*/
};                 /* struct dns_socket */

/*
 * NOTE: Actual closure delayed so that kqueue(2) and epoll(2) callers have
 * a chance to recognize a state change after installing a persistent event
 * and where sequential descriptors with the same integer value returned
 * from _pollfd() would be ambiguous. See dns_so_closefds().
 */
static int dns_so_closefd(struct dns_socket *so, int *fd) {
	int error;

	if (*fd == -1) return 0;

	if (so->opts.closefd.cb) {
		if ((error = so->opts.closefd.cb(fd, so->opts.closefd.arg))) {
			return error;
		} else if (*fd == -1) return 0;
	}

	if (!(so->onum < so->olim)) {
		unsigned olim = DNS_PP_MAX(4, so->olim * 2);
		void *old;

		if (!(old = realloc(so->old, sizeof so->old[0] * olim))) return dns_syerr();

		so->old = old;
		so->olim = olim;
	}

	so->old[so->onum++] = *fd;
	*fd = -1;

	return 0;
} /* dns_so_closefd() */

#define DNS_SO_CLOSE_UDP 0x01
#define DNS_SO_CLOSE_TCP 0x02
#define DNS_SO_CLOSE_OLD 0x04
#define DNS_SO_CLOSE_ALL (DNS_SO_CLOSE_UDP | DNS_SO_CLOSE_TCP | DNS_SO_CLOSE_OLD)

static void dns_so_closefds(struct dns_socket *so, int which) {
	if (DNS_SO_CLOSE_UDP & which) dns_socketclose(&so->udp, &so->opts);
	if (DNS_SO_CLOSE_TCP & which) dns_socketclose(&so->tcp, &so->opts);
	if (DNS_SO_CLOSE_OLD & which) {
		unsigned i;
		for (i = 0; i < so->onum; i++)
			dns_socketclose(&so->old[i], &so->opts);
		so->onum = 0;
		free(so->old);
		so->old = 0;
		so->olim = 0;
	}
} /* dns_so_closefds() */

static void dns_so_destroy(struct dns_socket *);

static struct dns_socket *
dns_so_init(struct dns_socket *so, const struct sockaddr *local, int type, const struct dns_options *opts, int *error) {
	static const struct dns_socket so_initializer = {.opts = DNS_OPTS_INITIALIZER, .udp = -1, .tcp = -1};

	*so = so_initializer;
	so->type = type;

	if (opts) so->opts = *opts;

	if (local) memcpy(&so->local, local, dns_sa_len(local));

	if (-1 == (so->udp = dns_socket((struct sockaddr *)&so->local, SOCK_DGRAM, error))) goto error;

	dns_k_permutor_init(&so->qids, 1, 65535);

	return so;
error:
	dns_so_destroy(so);

	return 0;
} /* dns_so_init() */

struct dns_socket *dns_so_open(const struct sockaddr *local, int type, const struct dns_options *opts, int *error) {
	struct dns_socket *so;

	if (!(so = malloc(sizeof *so))) goto syerr;

	if (!dns_so_init(so, local, type, opts, error)) goto error;

	return so;
syerr:
	*error = dns_syerr();
error:
	dns_so_close(so);

	return 0;
} /* dns_so_open() */

static void dns_so_destroy(struct dns_socket *so) {
	dns_so_reset(so);
	dns_so_closefds(so, DNS_SO_CLOSE_ALL);
} /* dns_so_destroy() */

void dns_so_close(struct dns_socket *so) {
	if (!so) return;

	dns_so_destroy(so);

	free(so);
} /* dns_so_close() */

void dns_so_reset(struct dns_socket *so) {
	dns_p_setptr(&so->answer, NULL);

	memset(&so->state, '\0', sizeof *so - offsetof(struct dns_socket, state));
} /* dns_so_reset() */

unsigned short dns_so_mkqid(struct dns_socket *so) {
	return dns_k_permutor_step(&so->qids);
} /* dns_so_mkqid() */

#define DNS_SO_MINBUF 768

static int dns_so_newanswer(struct dns_socket *so, size_t len) {
	size_t size = offsetof(struct dns_packet, data) + DNS_PP_MAX(len, DNS_SO_MINBUF);
	void *p;

	if (!(p = realloc(so->answer, size))) return dns_syerr();

	so->answer = dns_p_init(p, size);

	return 0;
} /* dns_so_newanswer() */

int dns_so_submit(struct dns_socket *so, struct dns_packet *Q, struct sockaddr *host) {
	struct dns_rr rr;
	int error = DNS_EUNKNOWN;

	dns_so_reset(so);

	if ((error = dns_rr_parse(&rr, 12, Q))) goto error;

	if (!(so->qlen = dns_d_expand(so->qname, sizeof so->qname, rr.dn.p, Q, &error))) goto error;
	/*
	 * NOTE: Don't bail if expansion is too long; caller may be
	 * intentionally sending long names. However, we won't be able to
	 * verify it on return.
	 */

	so->qtype = rr.type;
	so->qclass = rr.class;

	if ((error = dns_so_newanswer(so, (Q->memo.opt.maxudp) ? Q->memo.opt.maxudp : DNS_SO_MINBUF))) goto syerr;

	if (so->local.ss_family == AF_INET6 && host->sa_family == AF_INET) {
		socklen_t addrlen = sizeof(so->remote);
		uint32_t *addr = (uint32_t *)dns_sa_addr(AF_INET6, &so->remote, &addrlen);
		/* add v4mapping*/
		so->remote.ss_family = AF_INET6;
		addr[0] = 0;
		addr[1] = 0;
		addr[2] = ntohl(0xffff);
		addr[3] = ((struct sockaddr_in *)host)->sin_addr.s_addr;
		*dns_sa_port(AF_INET6, &so->remote) = ((struct sockaddr_in *)host)->sin_port;
	} else memcpy(&so->remote, host, dns_sa_len(host));

	so->query = Q;
	so->qout = 0;

	dns_begin(&so->elapsed);

	if (dns_header(so->query)->qid == 0) dns_header(so->query)->qid = dns_so_mkqid(so);

	so->qid = dns_header(so->query)->qid;
	so->state = (so->type == SOCK_STREAM) ? DNS_SO_TCP_INIT : DNS_SO_UDP_INIT;

	so->stat.queries++;

	return 0;
syerr:
	error = dns_syerr();
error:
	dns_so_reset(so);

	return error;
} /* dns_so_submit() */

static int dns_so_verify(struct dns_socket *so, struct dns_packet *P) {
	char qname[DNS_D_MAXNAME + 1];
	size_t qlen;
	struct dns_rr rr;
	int error = -1;

	if (so->qid != dns_header(so->answer)->qid) goto reject;

	if (!dns_p_count(so->answer, DNS_S_QD)) goto reject;

	if (0 != dns_rr_parse(&rr, 12, so->answer)) goto reject;

	if (rr.type != so->qtype || rr.class != so->qclass) goto reject;

	if (!(qlen = dns_d_expand(qname, sizeof qname, rr.dn.p, P, &error))) goto error;
	else if (qlen >= sizeof qname || qlen != so->qlen) goto reject;

	if (0 != strcasecmp(so->qname, qname)) goto reject;

	return 0;
reject:
	error = DNS_EUNKNOWN;
error:
	DNS_SHOW(P, "rejecting packet (%s)", dns_strerror(error));

	return error;
} /* dns_so_verify() */

static _Bool dns_so_tcp_keep(struct dns_socket *so) {
	struct sockaddr_storage remote;

	if (so->tcp == -1) return 0;

	if (0 != getpeername(so->tcp, (struct sockaddr *)&remote, &(socklen_t){sizeof remote})) return 0;

	return 0 == dns_sa_cmp(&remote, &so->remote);
} /* dns_so_tcp_keep() */

#if defined __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warray-bounds"
#endif

static int dns_so_tcp_send(struct dns_socket *so) {
	unsigned char *qsrc;
	size_t qend;
	long n;

	so->query->data[-2] = 0xff & (so->query->end >> 8);
	so->query->data[-1] = 0xff & (so->query->end >> 0);

	qsrc = &so->query->data[-2] + so->qout;
	qend = so->query->end + 2;

	while (so->qout < qend) {
		if (0 > (n = dns_send(so->tcp, (void *)&qsrc[so->qout], qend - so->qout, 0))) return dns_soerr();

		so->qout += n;
		so->stat.tcp.sent.bytes += n;
	}

	so->stat.tcp.sent.count++;

	return 0;
} /* dns_so_tcp_send() */

static int dns_so_tcp_recv(struct dns_socket *so) {
	unsigned char *asrc;
	size_t aend, alen;
	int error;
	long n;

	aend = so->alen + 2;

	while (so->apos < aend) {
		asrc = &so->answer->data[-2];

		if (0 > (n = recv(so->tcp, (void *)&asrc[so->apos], aend - so->apos, 0))) return dns_soerr();
		else if (n == 0) return DNS_EUNKNOWN; /* FIXME */

		so->apos += n;
		so->stat.tcp.rcvd.bytes += n;

		if (so->alen == 0 && so->apos >= 2) {
			alen = ((0xff & so->answer->data[-2]) << 8) | ((0xff & so->answer->data[-1]) << 0);

			if ((error = dns_so_newanswer(so, alen))) return error;

			so->alen = alen;
			aend = alen + 2;
		}
	}

	so->answer->end = so->alen;
	so->stat.tcp.rcvd.count++;

	return 0;
} /* dns_so_tcp_recv() */

#if __clang__
#pragma clang diagnostic pop
#endif

int dns_so_check(struct dns_socket *so) {
	struct sockaddr_storage tmp_ss;
	socklen_t tmp_ss_len = sizeof(tmp_ss);
	int error;
	long n;

retry:
	switch (so->state) {
		case DNS_SO_UDP_INIT:
			so->state++;
		case DNS_SO_UDP_CONN:
			memset(&tmp_ss, 0, sizeof(tmp_ss));
			connect(so->udp, (struct sockaddr *)&tmp_ss, sizeof(tmp_ss)); // Reset the previous connection
			if (so->opts.udp_uses_connect) {
				if (0 != connect(so->udp, (struct sockaddr *)&so->remote, dns_sa_len(&so->remote))) goto soerr;
			}

			so->state++;
		case DNS_SO_UDP_SEND:
			if (so->opts.udp_uses_connect) {
				if (0 > (n = send(so->udp, (void *)so->query->data, so->query->end, 0))) goto soerr;
			} else {
				if (0 > (n = sendto(so->udp, (void *)so->query->data, so->query->end, 0, (struct sockaddr *)&so->remote,
				                    dns_sa_len(&so->remote))))
					goto soerr;
			}

			so->stat.udp.sent.bytes += n;
			so->stat.udp.sent.count++;

			so->state++;
		case DNS_SO_UDP_RECV:
			if (so->opts.udp_uses_connect) {
				if (0 > (n = recv(so->udp, (void *)so->answer->data, so->answer->size, 0))) goto soerr;
			} else {
				memset(&tmp_ss, 0, sizeof(tmp_ss));
				tmp_ss_len = sizeof(tmp_ss);
				if (0 > (n = recvfrom(so->udp, (void *)so->answer->data, so->answer->size, 0,
				                      (struct sockaddr *)&tmp_ss, &tmp_ss_len)))
					goto soerr;
				if (memcmp(&tmp_ss, &so->remote, tmp_ss_len) != 0) {
					so->ip_differ = 1;
				}
			}

			so->stat.udp.rcvd.bytes += n;
			so->stat.udp.rcvd.count++;

			if ((so->answer->end = n) < 12) goto trash;

			if ((error = dns_so_verify(so, so->answer))) goto trash;

			so->state++;
		case DNS_SO_UDP_DONE:
			if (!dns_header(so->answer)->tc || so->type == SOCK_DGRAM) return 0;

			so->state++;
		case DNS_SO_TCP_INIT:
			if (dns_so_tcp_keep(so)) {
				so->state = DNS_SO_TCP_SEND;

				goto retry;
			}

			if ((error = dns_so_closefd(so, &so->tcp))) goto error;

			if (-1 == (so->tcp = dns_socket((struct sockaddr *)&so->local, SOCK_STREAM, &error))) goto error;

			so->state++;
		case DNS_SO_TCP_CONN:
			if (0 != connect(so->tcp, (struct sockaddr *)&so->remote, dns_sa_len(&so->remote))) {
				if (dns_soerr() != DNS_EISCONN) goto soerr;
			}

			so->state++;
		case DNS_SO_TCP_SEND:
			if ((error = dns_so_tcp_send(so))) goto error;

			so->state++;
		case DNS_SO_TCP_RECV:
			if ((error = dns_so_tcp_recv(so))) goto error;

			so->state++;
		case DNS_SO_TCP_DONE:
			/* close unless DNS_RESCONF_TCP_ONLY (see dns_res_tcp2type) */
			if (so->type != SOCK_STREAM) {
				if ((error = dns_so_closefd(so, &so->tcp))) goto error;
			}

			if (so->answer->end < 12) return DNS_EILLEGAL;

			if ((error = dns_so_verify(so, so->answer))) goto error;

			return 0;
		default:
			error = DNS_EUNKNOWN;

			goto error;
	} /* switch() */

trash:
	DNS_CARP("discarding packet");
	goto retry;
soerr:
	error = dns_soerr();

	goto error;
error:
	switch (error) {
		case DNS_EINTR:
			goto retry;
		case DNS_EINPROGRESS:
			/* FALL THROUGH */
		case DNS_EALREADY:
			/* FALL THROUGH */
#if DNS_EWOULDBLOCK != DNS_EAGAIN
		case DNS_EWOULDBLOCK:
			/* FALL THROUGH */
#endif
			error = DNS_EAGAIN;

			break;
	} /* switch() */

	return error;
} /* dns_so_check() */

struct dns_packet *dns_so_fetch(struct dns_socket *so, int *error) {
	struct dns_packet *answer;

	switch (so->state) {
		case DNS_SO_UDP_DONE:
		case DNS_SO_TCP_DONE:
			answer = so->answer;
			so->answer = 0;

			return answer;
		default:
			*error = DNS_EUNKNOWN;

			return 0;
	}
} /* dns_so_fetch() */

struct dns_packet *dns_so_query(struct dns_socket *so, struct dns_packet *Q, struct sockaddr *host, int *error_) {
	struct dns_packet *A;
	int error;

	if (!so->state) {
		if ((error = dns_so_submit(so, Q, host))) goto error;
	}

	if ((error = dns_so_check(so))) goto error;

	if (!(A = dns_so_fetch(so, &error))) goto error;

	dns_so_reset(so);

	return A;
error:
	*error_ = error;

	return 0;
} /* dns_so_query() */

time_t dns_so_elapsed(struct dns_socket *so) {
	return dns_elapsed(&so->elapsed);
} /* dns_so_elapsed() */

void dns_so_clear(struct dns_socket *so) {
	dns_so_closefds(so, DNS_SO_CLOSE_OLD);
} /* dns_so_clear() */

static int dns_so_events2(struct dns_socket *so, enum dns_events type) {
	int events = 0;

	switch (so->state) {
		case DNS_SO_UDP_CONN:
		case DNS_SO_UDP_SEND:
			events |= DNS_POLLOUT;

			break;
		case DNS_SO_UDP_RECV:
			events |= DNS_POLLIN;

			break;
		case DNS_SO_TCP_CONN:
		case DNS_SO_TCP_SEND:
			events |= DNS_POLLOUT;

			break;
		case DNS_SO_TCP_RECV:
			events |= DNS_POLLIN;

			break;
	} /* switch() */

	switch (type) {
		case DNS_LIBEVENT:
			return DNS_POLL2EV(events);
		default:
			return events;
	} /* switch() */
} /* dns_so_events2() */

int dns_so_events(struct dns_socket *so) {
	return dns_so_events2(so, so->opts.events);
} /* dns_so_events() */

int dns_so_pollfd(struct dns_socket *so) {
	switch (so->state) {
		case DNS_SO_UDP_CONN:
		case DNS_SO_UDP_SEND:
		case DNS_SO_UDP_RECV:
			return so->udp;
		case DNS_SO_TCP_CONN:
		case DNS_SO_TCP_SEND:
		case DNS_SO_TCP_RECV:
			return so->tcp;
	} /* switch() */

	return -1;
} /* dns_so_pollfd() */

int dns_so_poll(struct dns_socket *so, int timeout) {
	return dns_poll(dns_so_pollfd(so), dns_so_events2(so, DNS_SYSPOLL), timeout);
} /* dns_so_poll() */

const struct dns_stat *dns_so_stat(struct dns_socket *so) {
	return &so->stat;
} /* dns_so_stat() */

/*
 * R E S O L V E R  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

enum dns_res_state {
	DNS_R_INIT,
	DNS_R_GLUE,
	DNS_R_SWITCH, /* (B)IND, (F)ILE, (C)ACHE */

	DNS_R_FILE, /* Lookup in local hosts database */

	DNS_R_CACHE, /* Lookup in application cache */
	DNS_R_SUBMIT,
	DNS_R_CHECK,
	DNS_R_FETCH,

	DNS_R_BIND, /* Lookup in the network */
	DNS_R_SEARCH,
	DNS_R_HINTS,
	DNS_R_ITERATE,
	DNS_R_FOREACH_NS,
	DNS_R_RESOLV0_NS, /* Prologue: Setup next frame and recurse */
	DNS_R_RESOLV1_NS, /* Epilog: Inspect answer */
	DNS_R_FOREACH_A,
	DNS_R_QUERY_A,
	DNS_R_CNAME0_A,
	DNS_R_CNAME1_A,

	DNS_R_FINISH,
	DNS_R_SMART0_A,
	DNS_R_SMART1_A,
	DNS_R_DONE,
	DNS_R_SERVFAIL,
}; /* enum dns_res_state */

#define DNS_R_MAXDEPTH 8
#define DNS_R_ENDFRAME (DNS_R_MAXDEPTH - 1)

struct dns_resolver {
	struct dns_socket so;

	struct dns_resolv_conf *resconf;
	struct dns_hosts *hosts;
	struct dns_hints *hints;
	struct dns_cache *cache;

	dns_atomic_t refcount;

	/* Reset zeroes everything below here. */

	char qname[DNS_D_MAXNAME + 1];
	size_t qlen;

	enum dns_type qtype;
	enum dns_class qclass;

	struct dns_clock elapsed;

	dns_resconf_i_t search;

	struct dns_rr_i smart;

	struct dns_packet *nodata; /* answer if nothing better */

	unsigned sp;

	struct dns_res_frame {
		enum dns_res_state state;

		int error;
		int which; /* (B)IND, (F)ILE; index into resconf->lookup */
		int qflags;

		unsigned attempts;

		struct dns_packet *query, *answer, *hints;

		struct dns_rr_i hints_i, hints_j;
		struct dns_rr hints_ns, ans_cname;
	} stack[DNS_R_MAXDEPTH];

	unsigned char search_enabled;
}; /* struct dns_resolver */

static int dns_res_tcp2type(int tcp) {
	switch (tcp) {
		case DNS_RESCONF_TCP_ONLY:
			return SOCK_STREAM;
		case DNS_RESCONF_TCP_DISABLE:
			return SOCK_DGRAM;
		default:
			return 0;
	}
} /* dns_res_tcp2type() */

struct dns_resolver *dns_res_open(struct dns_resolv_conf *resconf,
                                  struct dns_hosts *hosts,
                                  struct dns_hints *hints,
                                  struct dns_cache *cache,
                                  const struct dns_options *opts,
                                  int *_error) {
	static const struct dns_resolver R_initializer = {
	    .refcount = 1,
	};
	struct dns_resolver *R = 0;
	int type, error;

	/*
	 * Grab ref count early because the caller may have passed us a mortal
	 * reference, and we want to do the right thing if we return early
	 * from an error.
	 */
	if (resconf) dns_resconf_acquire(resconf);
	if (hosts) dns_hosts_acquire(hosts);
	if (hints) dns_hints_acquire(hints);
	if (cache) dns_cache_acquire(cache);

	/*
	 * Don't try to load it ourselves because a NULL object might be an
	 * error from, say, dns_resconf_root(), and loading
	 * dns_resconf_local() by default would create undesirable surpises.
	 */
	if (!resconf || !hosts || !hints) goto _error;

	if (!(R = malloc(sizeof *R))) goto syerr;

	*R = R_initializer;
	type = dns_res_tcp2type(resconf->options.tcp);

	if (!dns_so_init(&R->so, (struct sockaddr *)&resconf->iface, type, opts, &error)) goto error;

	R->resconf = resconf;
	R->hosts = hosts;
	R->hints = hints;
	R->cache = cache;

	return R;
syerr:
	error = dns_syerr();
error:
	*_error = error;
_error:
	dns_res_close(R);

	dns_resconf_close(resconf);
	dns_hosts_close(hosts);
	dns_hints_close(hints);
	dns_cache_close(cache);

	return 0;
} /* dns_res_open() */

struct dns_resolver *dns_res_stub(const struct dns_options *opts, int *error) {
	struct dns_resolv_conf *resconf = 0;
	struct dns_hosts *hosts = 0;
	struct dns_hints *hints = 0;
	struct dns_resolver *res = 0;

	if (!(resconf = dns_resconf_local(error))) goto epilog;

	if (!(hosts = dns_hosts_local(error))) goto epilog;

	if (!(hints = dns_hints_local(resconf, error))) goto epilog;

	if (!(res = dns_res_open(resconf, hosts, hints, NULL, opts, error))) goto epilog;

epilog:
	dns_resconf_close(resconf);
	dns_hosts_close(hosts);
	dns_hints_close(hints);

	return res;
} /* dns_res_stub() */

static void dns_res_frame_destroy(struct dns_resolver *R, struct dns_res_frame *frame) {
	(void)R;

	dns_p_setptr(&frame->query, NULL);
	dns_p_setptr(&frame->answer, NULL);
	dns_p_setptr(&frame->hints, NULL);
} /* dns_res_frame_destroy() */

static void dns_res_frame_init(struct dns_resolver *R, struct dns_res_frame *frame) {
	memset(frame, '\0', sizeof *frame);
	if (R != NULL && R->resconf != NULL) {
		if (!R->resconf->options.recurse) frame->qflags |= DNS_Q_RD;
		if (R->resconf->options.edns0) frame->qflags |= DNS_Q_EDNS0;
	}
} /* dns_res_frame_init() */

static void dns_res_frame_reset(struct dns_resolver *R, struct dns_res_frame *frame) {
	dns_res_frame_destroy(R, frame);
	dns_res_frame_init(R, frame);
} /* dns_res_frame_reset() */

static dns_error_t dns_res_frame_prepare(
    struct dns_resolver *R, struct dns_res_frame *F, const char *qname, enum dns_type qtype, enum dns_class qclass) {
	struct dns_packet *P = NULL;

	if (!(F < endof(R->stack))) return DNS_EUNKNOWN;

	dns_p_movptr(&P, &F->query);
	dns_res_frame_reset(R, F);
	dns_p_movptr(&F->query, &P);

	return dns_q_make(&F->query, qname, qtype, qclass, F->qflags);
} /* dns_res_frame_prepare() */

void dns_res_reset(struct dns_resolver *R) {
	unsigned i;

	dns_so_reset(&R->so);
	dns_p_setptr(&R->nodata, NULL);

	for (i = 0; i < lengthof(R->stack); i++)
		dns_res_frame_destroy(R, &R->stack[i]);

	memset(&R->qname, '\0', sizeof *R - offsetof(struct dns_resolver, qname));

	for (i = 0; i < lengthof(R->stack); i++)
		dns_res_frame_init(R, &R->stack[i]);
} /* dns_res_reset() */

void dns_res_close(struct dns_resolver *R) {
	if (!R || 1 < dns_res_release(R)) return;

	dns_res_reset(R);

	dns_so_destroy(&R->so);

	dns_hints_close(R->hints);
	dns_hosts_close(R->hosts);
	dns_resconf_close(R->resconf);
	dns_cache_close(R->cache);

	free(R);
} /* dns_res_close() */

dns_refcount_t dns_res_acquire(struct dns_resolver *R) {
	return dns_atomic_fetch_add(&R->refcount);
} /* dns_res_acquire() */

dns_refcount_t dns_res_release(struct dns_resolver *R) {
	return dns_atomic_fetch_sub(&R->refcount);
} /* dns_res_release() */

struct dns_resolver *dns_res_mortal(struct dns_resolver *res) {
	if (res) dns_res_release(res);
	return res;
} /* dns_res_mortal() */

static struct dns_packet *dns_res_merge(struct dns_packet *P0, struct dns_packet *P1, int *error_) {
	size_t bufsiz = P0->end + P1->end;
	struct dns_packet *P[3] = {P0, P1, 0};
	struct dns_rr rr[3];
	int error, copy, i;
	enum dns_section section;

retry:
	if (!(P[2] = dns_p_make(bufsiz, &error))) goto error;

	dns_rr_foreach(&rr[0], P[0], .section = DNS_S_QD) {
		if ((error = dns_rr_copy(P[2], &rr[0], P[0]))) goto error;
	}

	for (section = DNS_S_AN; (DNS_S_ALL & section); section <<= 1) {
		for (i = 0; i < 2; i++) {
			dns_rr_foreach(&rr[i], P[i], .section = section) {
				copy = 1;

				dns_rr_foreach(&rr[2], P[2], .type = rr[i].type, .section = (DNS_S_ALL & ~DNS_S_QD)) {
					if (0 == dns_rr_cmp(&rr[i], P[i], &rr[2], P[2])) {
						copy = 0;

						break;
					}
				}

				if (copy && (error = dns_rr_copy(P[2], &rr[i], P[i]))) {
					if (error == DNS_ENOBUFS && bufsiz < 65535) {
						dns_p_setptr(&P[2], NULL);

						bufsiz = DNS_PP_MAX(65535, bufsiz * 2);

						goto retry;
					}

					goto error;
				}
			} /* foreach(rr) */
		}     /* foreach(packet) */
	}         /* foreach(section) */

	return P[2];
error:
	*error_ = error;

	dns_p_free(P[2]);

	return 0;
} /* dns_res_merge() */

static struct dns_packet *dns_res_glue(struct dns_resolver *R, struct dns_packet *Q) {
	struct dns_packet *P = dns_p_new(512);
	char qname[DNS_D_MAXNAME + 1];
	size_t qlen;
	enum dns_type qtype;
	struct dns_rr rr;
	unsigned sp;
	int error;

	if (!(qlen = dns_d_expand(qname, sizeof qname, 12, Q, &error)) || qlen >= sizeof qname) return 0;

	if (!(qtype = dns_rr_type(12, Q))) return 0;

	if ((error = dns_p_push(P, DNS_S_QD, qname, strlen(qname), qtype, DNS_C_IN, 0, 0))) return 0;

	for (sp = 0; sp <= R->sp; sp++) {
		if (!R->stack[sp].answer) continue;

		dns_rr_foreach(&rr, R->stack[sp].answer, .name = qname, .type = qtype, .section = (DNS_S_ALL & ~DNS_S_QD)) {
			rr.section = DNS_S_AN;

			if ((error = dns_rr_copy(P, &rr, R->stack[sp].answer))) return 0;
		}
	}

	if (dns_p_count(P, DNS_S_AN) > 0) goto copy;

	/* Otherwise, look for a CNAME */
	for (sp = 0; sp <= R->sp; sp++) {
		if (!R->stack[sp].answer) continue;

		dns_rr_foreach(&rr, R->stack[sp].answer, .name = qname, .type = DNS_T_CNAME,
		               .section = (DNS_S_ALL & ~DNS_S_QD)) {
			rr.section = DNS_S_AN;

			if ((error = dns_rr_copy(P, &rr, R->stack[sp].answer))) return 0;
		}
	}

	if (!dns_p_count(P, DNS_S_AN)) return 0;

copy:
	return dns_p_copy(dns_p_make(P->end, &error), P);
} /* dns_res_glue() */

/*
 * Sort NS records by three criteria:
 *
 * 	1) Whether glue is present.
 * 	2) Whether glue record is original or of recursive lookup.
 * 	3) Randomly shuffle records which share the above criteria.
 *
 * NOTE: Assumes only NS records passed, AND ASSUMES no new NS records will
 *       be added during an iteration.
 *
 * FIXME: Only groks A glue, not AAAA glue.
 */
static int dns_res_nameserv_cmp(struct dns_rr *a, struct dns_rr *b, struct dns_rr_i *i, struct dns_packet *P) {
	_Bool glued[2] = {0};
	struct dns_rr x = {0}, y = {0};
	struct dns_ns ns;
	int cmp, error;

	if (!(error = dns_ns_parse(&ns, a, P)))
		glued[0] = !!dns_rr_grep(
		    &x, 1, dns_rr_i_new(P, .section = (DNS_S_ALL & ~DNS_S_QD), .name = ns.host, .type = DNS_T_A), P, &error);

	if (!(error = dns_ns_parse(&ns, b, P)))
		glued[1] = !!dns_rr_grep(
		    &y, 1, dns_rr_i_new(P, .section = (DNS_S_ALL & ~DNS_S_QD), .name = ns.host, .type = DNS_T_A), P, &error);

	if ((cmp = glued[1] - glued[0])) {
		return cmp;
	} else if ((cmp = (dns_rr_offset(&y) < i->args[0]) - (dns_rr_offset(&x) < i->args[0]))) {
		return cmp;
	} else {
		return dns_rr_i_shuffle(a, b, i, P);
	}
} /* dns_res_nameserv_cmp() */

#define dgoto(sp, i)                                                                                                   \
	do {                                                                                                               \
		R->stack[(sp)].state = (i);                                                                                    \
		goto exec;                                                                                                     \
	} while (0)

static int dns_res_exec(struct dns_resolver *R) {
	struct dns_res_frame *F;
	struct dns_packet *P;
	union {
		char host[DNS_D_MAXNAME + 1];
		char name[DNS_D_MAXNAME + 1];
		struct dns_ns ns;
		struct dns_cname cname;
	} u;
	size_t len;
	struct dns_rr rr;
	int error;

exec:

	F = &R->stack[R->sp];

	switch (F->state) {
		case DNS_R_INIT:
			F->state++;
		case DNS_R_GLUE:
			if (R->sp == 0) dgoto(R->sp, DNS_R_SWITCH);

			if (!F->query) goto noquery;

			if (!(F->answer = dns_res_glue(R, F->query))) dgoto(R->sp, DNS_R_SWITCH);

			if (!(len = dns_d_expand(u.name, sizeof u.name, 12, F->query, &error))) goto error;
			else if (len >= sizeof u.name) goto toolong;

			dns_rr_foreach(&rr, F->answer, .name = u.name, .type = dns_rr_type(12, F->query), .section = DNS_S_AN) {
				dgoto(R->sp, DNS_R_FINISH);
			}

			dns_rr_foreach(&rr, F->answer, .name = u.name, .type = DNS_T_CNAME, .section = DNS_S_AN) {
				F->ans_cname = rr;

				dgoto(R->sp, DNS_R_CNAME0_A);
			}

			F->state++;
		case DNS_R_SWITCH:
			while (F->which < (int)sizeof R->resconf->lookup && R->resconf->lookup[F->which]) {
				switch (R->resconf->lookup[F->which++]) {
					case 'b':
					case 'B':
						dgoto(R->sp, DNS_R_BIND);
					case 'f':
					case 'F':
						dgoto(R->sp, DNS_R_FILE);
					case 'c':
					case 'C':
						if (R->cache) dgoto(R->sp, DNS_R_CACHE);

						break;
					default:
						break;
				}
			}

			/*
			 * FIXME: Examine more closely whether our logic is correct
			 * and DNS_R_SERVFAIL is the correct default response.
			 *
			 * Case 1: We got here because we never got an answer on the
			 *   wire. All queries timed-out and we reached maximum
			 *   attempts count. See DNS_R_FOREACH_NS. In that case
			 *   DNS_R_SERVFAIL is the correct state, unless we want to
			 *   return DNS_ETIMEDOUT.
			 *
			 * Case 2: We were a stub resolver and got an unsatisfactory
			 *   answer (empty ANSWER section) which caused us to jump
			 *   back to DNS_R_SEARCH and ultimately to DNS_R_SWITCH. We
			 *   return the answer returned from the wire, which we
			 *   stashed in R->nodata.
			 *
			 * Case 3: We reached maximum attempts count as in case #1,
			 *   but never got an authoritative response which caused us
			 *   to short-circuit. See end of DNS_R_QUERY_A case. We
			 *   should probably prepare R->nodata as in case #2.
			 */
			if (R->sp == 0 && R->nodata) { /* XXX: can we just return nodata regardless? */
				dns_p_movptr(&F->answer, &R->nodata);
				dgoto(R->sp, DNS_R_FINISH);
			}

			dgoto(R->sp, DNS_R_SERVFAIL);
		case DNS_R_FILE:
			if (R->sp > 0) {
				if (!dns_p_setptr(&F->answer, dns_hosts_query(R->hosts, F->query, &error))) goto error;

				if (dns_p_count(F->answer, DNS_S_AN) > 0) dgoto(R->sp, DNS_R_FINISH);

				dns_p_setptr(&F->answer, NULL);
			} else {
				R->search = 0;

				while ((len = dns_resconf_search(u.name, sizeof u.name, R->qname, R->qlen, R->resconf, &R->search))) {
					if ((error = dns_q_make2(&F->query, u.name, len, R->qtype, R->qclass, F->qflags))) goto error;

					if (!dns_p_setptr(&F->answer, dns_hosts_query(R->hosts, F->query, &error))) goto error;

					if (dns_p_count(F->answer, DNS_S_AN) > 0) dgoto(R->sp, DNS_R_FINISH);

					dns_p_setptr(&F->answer, NULL);
				}
			}

			dgoto(R->sp, DNS_R_SWITCH);
		case DNS_R_CACHE:
			error = 0;

			if (!F->query && (error = dns_q_make(&F->query, R->qname, R->qtype, R->qclass, F->qflags))) goto error;

			if (dns_p_setptr(&F->answer, R->cache->query(F->query, R->cache, &error))) {
				if (dns_p_count(F->answer, DNS_S_AN) > 0) dgoto(R->sp, DNS_R_FINISH);

				dns_p_setptr(&F->answer, NULL);

				dgoto(R->sp, DNS_R_SWITCH);
			} else if (error) goto error;

			F->state++;
		case DNS_R_SUBMIT:
			if ((error = R->cache->submit(F->query, R->cache))) goto error;

			F->state++;
		case DNS_R_CHECK:
			if ((error = R->cache->check(R->cache))) goto error;

			F->state++;
		case DNS_R_FETCH:
			error = 0;

			if (dns_p_setptr(&F->answer, R->cache->fetch(R->cache, &error))) {
				if (dns_p_count(F->answer, DNS_S_AN) > 0) dgoto(R->sp, DNS_R_FINISH);

				dns_p_setptr(&F->answer, NULL);

				dgoto(R->sp, DNS_R_SWITCH);
			} else if (error) goto error;

			dgoto(R->sp, DNS_R_SWITCH);
		case DNS_R_BIND:
			if (R->sp > 0) {
				if (!F->query) goto noquery;

				dgoto(R->sp, DNS_R_HINTS);
			}

			R->search = 0;

			F->state++;
		case DNS_R_SEARCH:
			/*
			 * XXX: We probably should only apply the domain search
			 * algorithm if R->sp == 0.
			 */
			if (!(len = dns_resconf_search(u.name, sizeof u.name, R->qname, R->qlen, R->resconf, &R->search)))
				dgoto(R->sp, DNS_R_SWITCH);

			if ((error = dns_q_make2(&F->query, u.name, len, R->qtype, R->qclass, F->qflags))) goto error;

			F->state++;
		case DNS_R_HINTS:
			if (!dns_p_setptr(&F->hints, dns_hints_query(R->hints, F->query, &error))) goto error;

			F->state++;
		case DNS_R_ITERATE:
			dns_rr_i_init(&F->hints_i, F->hints);

			F->hints_i.section = DNS_S_AUTHORITY;
			F->hints_i.type = DNS_T_NS;
			F->hints_i.sort = &dns_res_nameserv_cmp;
			F->hints_i.args[0] = F->hints->end;

			F->state++;
		case DNS_R_FOREACH_NS:
			dns_rr_i_save(&F->hints_i);

			/* Load our next nameserver host. */
			if (!dns_rr_grep(&F->hints_ns, 1, &F->hints_i, F->hints, &error)) {
				if (++F->attempts < R->resconf->options.attempts) dgoto(R->sp, DNS_R_ITERATE);

				dgoto(R->sp, DNS_R_SWITCH);
			}

			dns_rr_i_init(&F->hints_j, F->hints);

			/* Assume there are glue records */
			dgoto(R->sp, DNS_R_FOREACH_A);
		case DNS_R_RESOLV0_NS:
			/* Have we reached our max depth? */
			if (&F[1] >= endof(R->stack)) dgoto(R->sp, DNS_R_FOREACH_NS);

			if ((error = dns_ns_parse(&u.ns, &F->hints_ns, F->hints))) goto error;
			if ((error = dns_res_frame_prepare(R, &F[1], u.ns.host, DNS_T_A, DNS_C_IN))) goto error;

			F->state++;

			dgoto(++R->sp, DNS_R_INIT);
		case DNS_R_RESOLV1_NS:
			if (!(len = dns_d_expand(u.host, sizeof u.host, 12, F[1].query, &error))) goto error;
			else if (len >= sizeof u.host) goto toolong;

			dns_rr_foreach(&rr, F[1].answer, .name = u.host, .type = DNS_T_A, .section = (DNS_S_ALL & ~DNS_S_QD)) {
				rr.section = DNS_S_AR;

				if ((error = dns_rr_copy(F->hints, &rr, F[1].answer))) goto error;

				dns_rr_i_rewind(&F->hints_i); /* Now there's glue. */
			}

			dgoto(R->sp, DNS_R_FOREACH_NS);
		case DNS_R_FOREACH_A: {
			struct sockaddr_storage saddr;
			memset(&saddr, 0, sizeof(saddr));
			socklen_t saddr_len = sizeof(saddr);

			/*
			 * NOTE: Iterator initialized in DNS_R_FOREACH_NS because
			 * this state is re-entrant, but we need to reset
			 * .name to a valid pointer each time.
			 */
			if ((error = dns_ns_parse(&u.ns, &F->hints_ns, F->hints))) goto error;

			F->hints_j.name = u.ns.host;
			F->hints_j.type = DNS_T_ALL;
			F->hints_j.section = DNS_S_ALL & ~DNS_S_QD;

			if (!dns_rr_grep(&rr, 1, &F->hints_j, F->hints, &error)) {
				if (!dns_rr_i_count(&F->hints_j)) dgoto(R->sp, DNS_R_RESOLV0_NS);

				dgoto(R->sp, DNS_R_FOREACH_NS);
			}

			saddr.ss_family = rr.type == DNS_T_AAAA ? AF_INET6 : AF_INET;
			if (saddr.ss_family == AF_INET) {
				if ((error =
				         dns_a_parse((struct dns_a *)dns_sa_addr(saddr.ss_family, &saddr, &saddr_len), &rr, F->hints)))
					goto error;
			} else {
				if ((error = dns_aaaa_parse((struct dns_aaaa *)dns_sa_addr(saddr.ss_family, &saddr, &saddr_len), &rr,
				                            F->hints)))
					goto error;
			}

			if (R->sp == 0) dns_fill_sockaddr_from_hints(R->hints, saddr.ss_family, (struct sockaddr *)&saddr);
			else *dns_sa_port(saddr.ss_family, &saddr) = htons(53);

			if (DNS_DEBUG) {
				char addr[INET_ADDRSTRLEN + 1];
				if (saddr.ss_family == AF_INET)
					dns_a_print(addr, sizeof addr, (struct dns_a *)dns_sa_addr(saddr.ss_family, &saddr, &saddr_len));
				else
					dns_aaaa_print(addr, sizeof addr,
					               (struct dns_aaaa *)dns_sa_addr(saddr.ss_family, &saddr, &saddr_len));
				dns_header(F->query)->qid = dns_so_mkqid(&R->so);
				DNS_SHOW(F->query, "ASKING: %s/%s @ DEPTH: %u)", u.ns.host, addr, R->sp);
			}

			if ((error = dns_so_submit(&R->so, F->query, (struct sockaddr *)&saddr))) goto error;

			F->state++;
		}
		case DNS_R_QUERY_A:
			if (dns_so_elapsed(&R->so) >= dns_resconf_timeout(R->resconf)) dgoto(R->sp, DNS_R_FOREACH_A);

			if ((error = dns_so_check(&R->so)) != 0) {
				if (error == DNS_ENETUNREACH || error == DNS_ECONNREFUSED || error == DNS_ECONNRESET ||
				    error == EINVAL || error == DNS_EHOSTUNREACH) { /* maybe even more case*/
					char remote_sock[64];
					struct sockaddr *addr = (struct sockaddr *)&R->so.remote;
					bctbx_sockaddr_to_printable_ip_address(addr, dns_sa_len(addr), remote_sock, sizeof(remote_sock));
					belle_sip_error("Cannot reach [%s] because [%s]", remote_sock, strerror(error));
					dgoto(R->sp, DNS_R_FOREACH_A);
				} else goto error;
			}
			if (!dns_p_setptr(&F->answer, dns_so_fetch(&R->so, &error))) goto error;

			if (DNS_DEBUG) {
				DNS_SHOW(F->answer, "ANSWER @ DEPTH: %u)", R->sp);
			}

			if (dns_p_rcode(F->answer) == DNS_RC_FORMERR || dns_p_rcode(F->answer) == DNS_RC_NOTIMP ||
			    dns_p_rcode(F->answer) == DNS_RC_BADVERS) {
				/* Temporarily disable EDNS0 and try again. */
				if (F->qflags & DNS_Q_EDNS0) {
					F->qflags &= ~DNS_Q_EDNS0;
					if ((error = dns_q_remake(&F->query, F->qflags))) goto error;

					dgoto(R->sp, DNS_R_FOREACH_A);
				}
			}

			if (dns_p_rcode(F->answer) == DNS_RC_REFUSED) {
				dgoto(R->sp, DNS_R_FOREACH_A);
			}

			if ((error = dns_rr_parse(&rr, 12, F->query))) goto error;

			if (!(len = dns_d_expand(u.name, sizeof u.name, rr.dn.p, F->query, &error))) goto error;
			else if (len >= sizeof u.name) goto toolong;

			dns_rr_foreach(&rr, F->answer, .section = DNS_S_AN, .name = u.name, .type = rr.type) {
				dgoto(R->sp, DNS_R_FINISH); /* Found */
			}

			dns_rr_foreach(&rr, F->answer, .section = DNS_S_AN, .name = u.name, .type = DNS_T_CNAME) {
				F->ans_cname = rr;

				dgoto(R->sp, DNS_R_CNAME0_A);
			}

			/*
			 * XXX: The condition here should probably check whether
			 * R->sp == 0, because DNS_R_SEARCH runs regardless of
			 * options.recurse. See DNS_R_BIND.
			 */
			if (!R->resconf->options.recurse) {
				/* Make first answer our tentative answer */
				if (!R->nodata) dns_p_movptr(&R->nodata, &F->answer);

				if (R->search_enabled) dgoto(R->sp, DNS_R_SEARCH);
				else dgoto(R->sp, DNS_R_FINISH);
			}

			dns_rr_foreach(&rr, F->answer, .section = DNS_S_NS, .type = DNS_T_NS) {
				dns_p_movptr(&F->hints, &F->answer);

				dgoto(R->sp, DNS_R_ITERATE);
			}

			/* XXX: Should this go further up? */
			if (dns_header(F->answer)->aa) dgoto(R->sp, DNS_R_FINISH);

			/* XXX: Should we copy F->answer to R->nodata? */

			dgoto(R->sp, DNS_R_FOREACH_A);
		case DNS_R_CNAME0_A:
			if (&F[1] >= endof(R->stack)) dgoto(R->sp, DNS_R_FINISH);

			if ((error = dns_cname_parse(&u.cname, &F->ans_cname, F->answer))) goto error;
			if ((error = dns_res_frame_prepare(R, &F[1], u.cname.host, dns_rr_type(12, F->query), DNS_C_IN)))
				goto error;

			F->state++;

			dgoto(++R->sp, DNS_R_INIT);
		case DNS_R_CNAME1_A:
			if (!(P = dns_res_merge(F->answer, F[1].answer, &error))) goto error;

			dns_p_setptr(&F->answer, P);

			dgoto(R->sp, DNS_R_FINISH);
		case DNS_R_FINISH:
			if (!F->answer) goto noanswer;

			if (!R->resconf->options.smart || R->sp > 0) dgoto(R->sp, DNS_R_DONE);

			R->smart.section = DNS_S_AN;
			R->smart.type = R->qtype;

			dns_rr_i_init(&R->smart, F->answer);

			F->state++;
		case DNS_R_SMART0_A:
			if (&F[1] >= endof(R->stack)) dgoto(R->sp, DNS_R_DONE);

			while (dns_rr_grep(&rr, 1, &R->smart, F->answer, &error)) {
				union {
					struct dns_ns ns;
					struct dns_mx mx;
					struct dns_srv srv;
				} rd;
				const char *qname;
				enum dns_type qtype;
				enum dns_class qclass;

				switch (rr.type) {
					case DNS_T_NS:
						if ((error = dns_ns_parse(&rd.ns, &rr, F->answer))) goto error;

						qname = rd.ns.host;
						qtype = DNS_T_A;
						qclass = DNS_C_IN;

						break;
					case DNS_T_MX:
						if ((error = dns_mx_parse(&rd.mx, &rr, F->answer))) goto error;

						qname = rd.mx.host;
						qtype = DNS_T_A;
						qclass = DNS_C_IN;

						break;
					case DNS_T_SRV:
						if ((error = dns_srv_parse(&rd.srv, &rr, F->answer))) goto error;

						qname = rd.srv.target;
						qtype = DNS_T_A;
						qclass = DNS_C_IN;

						break;
					default:
						continue;
				} /* switch() */

				if ((error = dns_res_frame_prepare(R, &F[1], qname, qtype, qclass))) goto error;

				F->state++;

				dgoto(++R->sp, DNS_R_INIT);
			} /* while() */

			/*
			 * NOTE: SMTP specification says to fallback to A record.
			 *
			 * XXX: Should we add a mock MX answer?
			 */
			if (R->qtype == DNS_T_MX && R->smart.state.count == 0) {
				if ((error = dns_res_frame_prepare(R, &F[1], R->qname, DNS_T_A, DNS_C_IN))) goto error;

				R->smart.state.count++;
				F->state++;

				dgoto(++R->sp, DNS_R_INIT);
			}

			dgoto(R->sp, DNS_R_DONE);
		case DNS_R_SMART1_A:
			if (!F[1].answer) goto noanswer;

			/*
			 * FIXME: For CNAME chains (which are typically illegal in
			 * this context), we should rewrite the record host name
			 * to the original smart qname. All the user cares about
			 * is locating that A/AAAA record.
			 */
			dns_rr_foreach(&rr, F[1].answer, .section = DNS_S_AN, .type = DNS_T_A) {
				rr.section = DNS_S_AR;

				if (dns_rr_exists(&rr, F[1].answer, F->answer)) continue;

				while ((error = dns_rr_copy(F->answer, &rr, F[1].answer))) {
					if (error != DNS_ENOBUFS) goto error;
					if ((error = dns_p_grow(&F->answer))) goto error;
				}
			}

			dgoto(R->sp, DNS_R_SMART0_A);
		case DNS_R_DONE:
			if (!F->answer) goto noanswer;

			if (R->sp > 0) dgoto(--R->sp, F[-1].state);

			break;
		case DNS_R_SERVFAIL:
			if (!dns_p_setptr(&F->answer, dns_p_make(DNS_P_QBUFSIZ, &error))) goto error;

			dns_header(F->answer)->qr = 1;
			dns_header(F->answer)->rcode = DNS_RC_SERVFAIL;

			if ((error = dns_p_push(F->answer, DNS_S_QD, R->qname, strlen(R->qname), R->qtype, R->qclass, 0, 0)))
				goto error;

			dgoto(R->sp, DNS_R_DONE);
		default:
			error = EINVAL;

			goto error;
	} /* switch () */

	return 0;
noquery:
	error = DNS_ENOQUERY;

	goto error;
noanswer:
	error = DNS_ENOANSWER;

	goto error;
toolong:
	error = DNS_EILLEGAL;

	/* FALL THROUGH */
error:
	return error;
} /* dns_res_exec() */

#undef goto

void dns_res_clear(struct dns_resolver *R) {
	switch (R->stack[R->sp].state) {
		case DNS_R_CHECK:
			R->cache->clear(R->cache);
			break;
		default:
			dns_so_clear(&R->so);
			break;
	}
} /* dns_res_clear() */

static int dns_res_events2(struct dns_resolver *R, enum dns_events type) {
	int events;

	switch (R->stack[R->sp].state) {
		case DNS_R_CHECK:
			events = R->cache->events(R->cache);

			return (type == DNS_LIBEVENT) ? DNS_POLL2EV(events) : events;
		default:
			return dns_so_events2(&R->so, type);
	}
} /* dns_res_events2() */

int dns_res_events(struct dns_resolver *R) {
	return dns_res_events2(R, R->so.opts.events);
} /* dns_res_events() */

int dns_res_pollfd(struct dns_resolver *R) {
	switch (R->stack[R->sp].state) {
		case DNS_R_CHECK:
			return R->cache->pollfd(R->cache);
		default:
			return dns_so_pollfd(&R->so);
	}
} /* dns_res_pollfd() */

time_t dns_res_timeout(struct dns_resolver *R) {
	time_t elapsed;

	switch (R->stack[R->sp].state) {
#if 0
	case DNS_R_QUERY_AAAA:
#endif
		case DNS_R_QUERY_A:
			elapsed = dns_so_elapsed(&R->so);

			if (elapsed <= dns_resconf_timeout(R->resconf)) return R->resconf->options.timeout - elapsed;

			break;
		default:
			break;
	} /* switch() */

	/*
	 * NOTE: We're not in a pollable state, or the user code hasn't
	 * called dns_res_check properly. The calling code is probably
	 * broken. Put them into a slow-burn pattern.
	 */
	return 1;
} /* dns_res_timeout() */

time_t dns_res_elapsed(struct dns_resolver *R) {
	return dns_elapsed(&R->elapsed);
} /* dns_res_elapsed() */

int dns_res_poll(struct dns_resolver *R, int timeout) {
	return dns_poll(dns_res_pollfd(R), dns_res_events2(R, DNS_SYSPOLL), timeout);
} /* dns_res_poll() */

int dns_res_submit2(
    struct dns_resolver *R, const char *qname, size_t qlen, enum dns_type qtype, enum dns_class qclass) {
	dns_res_reset(R);

	/* Don't anchor; that can conflict with searchlist generation. */
	dns_d_init(R->qname, sizeof R->qname, qname, (R->qlen = qlen), 0);

	R->qtype = qtype;
	R->qclass = qclass;

	dns_begin(&R->elapsed);

	return 0;
} /* dns_res_submit2() */

int dns_res_submit(struct dns_resolver *R, const char *qname, enum dns_type qtype, enum dns_class qclass) {
	return dns_res_submit2(R, qname, strlen(qname), qtype, qclass);
} /* dns_res_submit() */

int dns_res_check(struct dns_resolver *R) {
	int error;

	if (R->stack[0].state != DNS_R_DONE) {
		if ((error = dns_res_exec(R))) return error;
	}

	return 0;
} /* dns_res_check() */

struct dns_packet *dns_res_fetch(struct dns_resolver *R, int *error) {
	struct dns_packet *P = NULL;

	if (R->stack[0].state != DNS_R_DONE) {
		*error = DNS_EUNKNOWN;
		return NULL;
	}

	if (!dns_p_movptr(&P, &R->stack[0].answer)) {
		*error = DNS_EFETCHED;
		return NULL;
	}

	return P;
} /* dns_res_fetch() */

static struct dns_packet *dns_res_fetch_and_study(struct dns_resolver *R, int *_error) {
	struct dns_packet *P = NULL;
	int error;

	if (!(P = dns_res_fetch(R, &error))) goto error;
	if ((error = dns_p_study(P))) goto error;

	return P;
error:
	*_error = error;

	dns_p_free(P);

	return NULL;
} /* dns_res_fetch_and_study() */

struct dns_packet *dns_res_query(
    struct dns_resolver *res, const char *qname, enum dns_type qtype, enum dns_class qclass, int timeout, int *error_) {
	int error;

	if ((error = dns_res_submit(res, qname, qtype, qclass))) goto error;

	while ((error = dns_res_check(res))) {
		if (dns_res_elapsed(res) > timeout) error = DNS_ETIMEDOUT;

		if (error != DNS_EAGAIN) goto error;

		if ((error = dns_res_poll(res, 1))) goto error;
	}

	return dns_res_fetch(res, error_);
error:
	*error_ = error;

	return 0;
} /* dns_res_query() */

const struct dns_stat *dns_res_stat(struct dns_resolver *res) {
	return dns_so_stat(&res->so);
} /* dns_res_stat() */

void dns_res_sethints(struct dns_resolver *res, struct dns_hints *hints) {
	dns_hints_acquire(hints); /* acquire first in case same hints object */
	dns_hints_close(res->hints);
	res->hints = hints;
} /* dns_res_sethints() */

void dns_res_enable_search(struct dns_resolver *res, unsigned char enable) {
	res->search_enabled = enable;
}

int dns_res_was_asymetric(struct dns_resolver *res) {
	return res->so.ip_differ;
}

/*
 * A D D R I N F O  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

struct dns_addrinfo {
	struct addrinfo hints;
	struct dns_resolver *res;

	char qname[DNS_D_MAXNAME + 1];
	enum dns_type qtype;
	unsigned short qport, port;

	struct {
		unsigned long todo;
		int atype;
		enum dns_type qtype;
	} af;

	struct dns_packet *answer;
	struct dns_packet *glue;

	struct dns_rr_i i, g;
	struct dns_rr rr;

	char cname[DNS_D_MAXNAME + 1];
	char i_cname[DNS_D_MAXNAME + 1], g_cname[DNS_D_MAXNAME + 1];

	int state;
	int found;

	struct dns_stat st;
}; /* struct dns_addrinfo */

#define DNS_AI_AFMAX 32
#define DNS_AI_AF2INDEX(af) (1UL << ((af)-1))

static int dns_ai_nextaf(struct dns_addrinfo *ai) {
	int qtype = 0, atype = 0;
	unsigned i;

	dns_static_assert(AF_UNSPEC == 0, "AF_UNSPEC constant not 0");
	dns_static_assert(AF_INET <= DNS_AI_AFMAX, "AF_INET constant too large");
	dns_static_assert(AF_INET6 <= DNS_AI_AFMAX, "AF_INET6 constant too large");

	for (i = 0; i < lengthof(ai->res->resconf->family); i++) {
		int af = ai->res->resconf->family[i];

		if (af == AF_UNSPEC) break;
		if (af < 0 || af > DNS_AI_AFMAX) continue;
		if (!(DNS_AI_AF2INDEX(af) & ai->af.todo)) continue;

		switch (af) {
			case AF_INET:
				atype = AF_INET;
				qtype = DNS_T_A;
				goto update;
			case AF_INET6:
				atype = AF_INET6;
				qtype = DNS_T_AAAA;
				goto update;
		}
	}

update:
	ai->af.atype = atype;
	ai->af.qtype = qtype;

	if (atype) ai->af.todo &= ~DNS_AI_AF2INDEX(atype);

	return atype;
} /* dns_ai_nextaf() */

static enum dns_type dns_ai_qtype(struct dns_addrinfo *ai) {
	return (ai->qtype) ? ai->qtype : ai->af.qtype;
} /* dns_ai_qtype() */

static dns_error_t dns_ai_parseport(unsigned short *port, const char *serv, const struct addrinfo *hints) {
	const char *cp = serv;
	unsigned long n = 0;

	while (*cp >= '0' && *cp <= '9' && n < 65536) {
		n *= 10;
		n += *cp++ - '0';
	}

	if (*cp == '\0') {
		if (cp == serv || n >= 65536) return DNS_ESERVICE;

		*port = n;

		return 0;
	}

	if (hints->ai_flags & AI_NUMERICSERV) return DNS_ESERVICE;

	/* TODO: try getaddrinfo(NULL, serv, { .ai_flags = AI_NUMERICSERV }) */

	return DNS_ESERVICE;
} /* dns_ai_parseport() */

struct dns_addrinfo *dns_ai_open(const char *host,
                                 const char *serv,
                                 enum dns_type qtype,
                                 const struct addrinfo *hints,
                                 struct dns_resolver *res,
                                 int *error_) {
	static const struct dns_addrinfo ai_initializer;
	struct dns_addrinfo *ai;
	int error;

	if (res) {
		dns_res_acquire(res);
	} else if (!(hints->ai_flags & AI_NUMERICHOST)) {
		/*
		 * NOTE: it's assumed that *_error is set from a previous
		 * API function call, such as dns_res_stub(). Should change
		 * this semantic, but it's applied elsewhere, too.
		 */
		return NULL;
	}

	if (!(ai = malloc(sizeof *ai))) goto syerr;

	*ai = ai_initializer;
	ai->hints = *hints;

	ai->res = res;
	res = NULL;

	if (sizeof ai->qname <= dns_strlcpy(ai->qname, host, sizeof ai->qname)) {
		error = ENAMETOOLONG;
		goto error;
	}

	ai->qtype = qtype;
	ai->qport = 0;

	if (serv && (error = dns_ai_parseport(&ai->qport, serv, hints))) goto error;
	ai->port = ai->qport;

	switch (ai->qtype) {
		case DNS_T_A:
			ai->af.todo = DNS_AI_AF2INDEX(AF_INET);
			break;
		case DNS_T_AAAA:
			ai->af.todo = DNS_AI_AF2INDEX(AF_INET6);
			break;
		default: /* 0, MX, SRV, etc */
			switch (ai->hints.ai_family) {
				case AF_UNSPEC:
					ai->af.todo = DNS_AI_AF2INDEX(AF_INET) | DNS_AI_AF2INDEX(AF_INET6);
					break;
				case AF_INET:
					ai->af.todo = DNS_AI_AF2INDEX(AF_INET);
					break;
				case AF_INET6:
					ai->af.todo = DNS_AI_AF2INDEX(AF_INET6);
					break;
				default:
					break;
			}
	}

	return ai;
syerr:
	error = dns_syerr();
error:
	*error_ = error;

	dns_ai_close(ai);
	dns_res_close(res);

	return NULL;
} /* dns_ai_open() */

void dns_ai_close(struct dns_addrinfo *ai) {
	if (!ai) return;

	dns_res_close(ai->res);

	if (ai->answer != ai->glue) dns_p_free(ai->glue);

	dns_p_free(ai->answer);
	free(ai);
} /* dns_ai_close() */

static int dns_ai_setent(struct addrinfo **ent, union dns_any *any, enum dns_type type, struct dns_addrinfo *ai) {
	struct sockaddr *saddr;
	struct sockaddr_in sin;
	struct sockaddr_in6 sin6;
	const char *cname;
	size_t clen;

	switch (type) {
		case DNS_T_A:
			saddr = memset(&sin, '\0', sizeof sin);

			sin.sin_family = AF_INET;
			sin.sin_port = htons(ai->port);

			memcpy(&sin.sin_addr, any, sizeof sin.sin_addr);

			break;
		case DNS_T_AAAA:
			saddr = memset(&sin6, '\0', sizeof sin6);

			sin6.sin6_family = AF_INET6;
			sin6.sin6_port = htons(ai->port);

			memcpy(&sin6.sin6_addr, any, sizeof sin6.sin6_addr);

			break;
		default:
			return EINVAL;
	} /* switch() */

	if (ai->hints.ai_flags & AI_CANONNAME) {
		cname = (*ai->cname) ? ai->cname : ai->qname;
		clen = strlen(cname);
	} else {
		cname = NULL;
		clen = 0;
	}

	if (!(*ent = malloc(sizeof **ent + dns_sa_len(saddr) + ((ai->hints.ai_flags & AI_CANONNAME) ? clen + 1 : 0))))
		return dns_syerr();

	memset(*ent, '\0', sizeof **ent);

	(*ent)->ai_family = saddr->sa_family;
	(*ent)->ai_socktype = ai->hints.ai_socktype;
	(*ent)->ai_protocol = ai->hints.ai_protocol;

	(*ent)->ai_addr = memcpy((unsigned char *)*ent + sizeof **ent, saddr, dns_sa_len(saddr));
	(*ent)->ai_addrlen = dns_sa_len(saddr);

	if (ai->hints.ai_flags & AI_CANONNAME)
		(*ent)->ai_canonname = memcpy((unsigned char *)*ent + sizeof **ent + dns_sa_len(saddr), cname, clen + 1);

	ai->found++;

	return 0;
} /* dns_ai_setent() */

enum dns_ai_state {
	DNS_AI_S_INIT,
	DNS_AI_S_NEXTAF,
	DNS_AI_S_NUMERIC,
	DNS_AI_S_SUBMIT,
	DNS_AI_S_CHECK,
	DNS_AI_S_FETCH,
	DNS_AI_S_FOREACH_I,
	DNS_AI_S_ITERATE_G,
	DNS_AI_S_FOREACH_G,
	DNS_AI_S_SUBMIT_G,
	DNS_AI_S_CHECK_G,
	DNS_AI_S_FETCH_G,
	DNS_AI_S_DONE,
}; /* enum dns_ai_state */

#define dns_ai_goto(which)                                                                                             \
	do {                                                                                                               \
		ai->state = (which);                                                                                           \
		goto exec;                                                                                                     \
	} while (0)

int dns_ai_nextent(struct addrinfo **ent, struct dns_addrinfo *ai) {
	struct dns_packet *ans, *glue;
	struct dns_rr rr;
	char qname[DNS_D_MAXNAME + 1];
	union dns_any any;
	size_t qlen, clen;
	int error;

	*ent = 0;

exec:

	switch (ai->state) {
		case DNS_AI_S_INIT:
			ai->state++;
		case DNS_AI_S_NEXTAF:
			if (!dns_ai_nextaf(ai)) dns_ai_goto(DNS_AI_S_DONE);

			ai->state++;
		case DNS_AI_S_NUMERIC:
			if (1 == dns_inet_pton(AF_INET, ai->qname, &any.a)) {
				if (ai->af.atype == AF_INET) {
					ai->state = DNS_AI_S_NEXTAF;
					return dns_ai_setent(ent, &any, DNS_T_A, ai);
				} else {
					dns_ai_goto(DNS_AI_S_NEXTAF);
				}
			}

			if (1 == dns_inet_pton(AF_INET6, ai->qname, &any.aaaa)) {
				if (ai->af.atype == AF_INET6) {
					ai->state = DNS_AI_S_NEXTAF;
					return dns_ai_setent(ent, &any, DNS_T_AAAA, ai);
				} else {
					dns_ai_goto(DNS_AI_S_NEXTAF);
				}
			}

			if (ai->hints.ai_flags & AI_NUMERICHOST) dns_ai_goto(DNS_AI_S_NEXTAF);

			ai->state++;
		case DNS_AI_S_SUBMIT:
			assert(ai->res);

			if ((error = dns_res_submit(ai->res, ai->qname, dns_ai_qtype(ai), DNS_C_IN))) return error;

			ai->state++;
		case DNS_AI_S_CHECK:
			if ((error = dns_res_check(ai->res))) return error;

			ai->state++;
		case DNS_AI_S_FETCH:
			if (!(ans = dns_res_fetch_and_study(ai->res, &error))) return error;
			if (ai->glue != ai->answer) dns_p_free(ai->glue);
			ai->glue = dns_p_movptr(&ai->answer, &ans);

			/* Search generator may have changed the qname. */
			if (!(qlen = dns_d_expand(qname, sizeof qname, 12, ai->answer, &error))) return error;
			else if (qlen >= sizeof qname) return DNS_EILLEGAL;
			if (!dns_d_cname(ai->cname, sizeof ai->cname, qname, qlen, ai->answer, &error)) return error;

			dns_strlcpy(ai->i_cname, ai->cname, sizeof ai->i_cname);
			dns_rr_i_init(&ai->i, ai->answer);
			ai->i.section = DNS_S_AN;
			ai->i.name = ai->i_cname;
			ai->i.type = dns_ai_qtype(ai);
			ai->i.sort = &dns_rr_i_order;

			ai->state++;
		case DNS_AI_S_FOREACH_I:
			if (!dns_rr_grep(&rr, 1, &ai->i, ai->answer, &error)) dns_ai_goto(DNS_AI_S_NEXTAF);

			if ((error = dns_any_parse(&any, &rr, ai->answer))) return error;

			ai->port = ai->qport;

			switch (rr.type) {
				case DNS_T_A:
				case DNS_T_AAAA:
					return dns_ai_setent(ent, &any, rr.type, ai);
				default:
					if (!(clen = dns_any_cname(ai->cname, sizeof ai->cname, &any, rr.type)))
						dns_ai_goto(DNS_AI_S_FOREACH_I);

					/*
					 * Find the "real" canonical name. Some authorities
					 * publish aliases where an RFC defines a canonical
					 * name. We trust that the resolver followed any
					 * CNAME chains on it's own, regardless of whether
					 * the "smart" option is enabled.
					 */
					if (!dns_d_cname(ai->cname, sizeof ai->cname, ai->cname, clen, ai->answer, &error)) return error;

					if (rr.type == DNS_T_SRV) ai->port = any.srv.port;

					break;
			} /* switch() */

			ai->state++;
		case DNS_AI_S_ITERATE_G:
			dns_strlcpy(ai->g_cname, ai->cname, sizeof ai->g_cname);
			dns_rr_i_init(&ai->g, ai->glue);
			ai->g.section = DNS_S_ALL & ~DNS_S_QD;
			ai->g.name = ai->g_cname;
			ai->g.type = ai->af.qtype;

			ai->state++;
		case DNS_AI_S_FOREACH_G:
			if (!dns_rr_grep(&rr, 1, &ai->g, ai->glue, &error)) {
				if (dns_rr_i_count(&ai->g) > 0) dns_ai_goto(DNS_AI_S_FOREACH_I);
				else dns_ai_goto(DNS_AI_S_SUBMIT_G);
			}

			if ((error = dns_any_parse(&any, &rr, ai->glue))) return error;

			return dns_ai_setent(ent, &any, rr.type, ai);
		case DNS_AI_S_SUBMIT_G:
			/* skip if already queried */
			if (dns_rr_grep(&rr, 1, dns_rr_i_new(ai->glue, .section = DNS_S_QD, .name = ai->g.name, .type = ai->g.type),
			                ai->glue, &error))
				dns_ai_goto(DNS_AI_S_FOREACH_I);

			if ((error = dns_res_submit(ai->res, ai->g.name, ai->g.type, DNS_C_IN))) return error;

			ai->state++;
		case DNS_AI_S_CHECK_G:
			if ((error = dns_res_check(ai->res))) return error;

			ai->state++;
		case DNS_AI_S_FETCH_G:
			if (!(ans = dns_res_fetch_and_study(ai->res, &error))) return error;

			glue = dns_p_merge(ai->glue, DNS_S_ALL, ans, DNS_S_ALL, &error);
			dns_p_setptr(&ans, NULL);
			if (!glue) return error;

			if (ai->glue != ai->answer) dns_p_free(ai->glue);
			ai->glue = glue;

			if (!dns_d_cname(ai->cname, sizeof ai->cname, ai->g.name, strlen(ai->g.name), ai->glue, &error))
				dns_ai_goto(DNS_AI_S_FOREACH_I);

			dns_ai_goto(DNS_AI_S_ITERATE_G);
		case DNS_AI_S_DONE:
			if (ai->found) {
				return ENOENT; /* TODO: Just return 0 */
			} else if (ai->answer) {
				switch (dns_p_rcode(ai->answer)) {
					case DNS_RC_NOERROR:
						/* FALL THROUGH */
					case DNS_RC_NXDOMAIN:
						return DNS_ENONAME;
					default:
						return DNS_EFAIL;
				}
			} else {
				return DNS_EFAIL;
			}
		default:
			return EINVAL;
	} /* switch() */
} /* dns_ai_nextent() */

time_t dns_ai_elapsed(struct dns_addrinfo *ai) {
	return (ai->res) ? dns_res_elapsed(ai->res) : 0;
} /* dns_ai_elapsed() */

void dns_ai_clear(struct dns_addrinfo *ai) {
	if (ai->res) dns_res_clear(ai->res);
} /* dns_ai_clear() */

int dns_ai_events(struct dns_addrinfo *ai) {
	return (ai->res) ? dns_res_events(ai->res) : 0;
} /* dns_ai_events() */

int dns_ai_pollfd(struct dns_addrinfo *ai) {
	return (ai->res) ? dns_res_pollfd(ai->res) : -1;
} /* dns_ai_pollfd() */

time_t dns_ai_timeout(struct dns_addrinfo *ai) {
	return (ai->res) ? dns_res_timeout(ai->res) : 0;
} /* dns_ai_timeout() */

int dns_ai_poll(struct dns_addrinfo *ai, int timeout) {
	return (ai->res) ? dns_res_poll(ai->res, timeout) : 0;
} /* dns_ai_poll() */

size_t dns_ai_print(void *_dst, size_t lim, struct addrinfo *ent, struct dns_addrinfo *ai) {
	struct dns_buf dst = DNS_B_INTO(_dst, lim);
	char addr[DNS_PP_MAX(INET_ADDRSTRLEN, INET6_ADDRSTRLEN) + 1];

	dns_b_puts(&dst, "[ ");
	dns_b_puts(&dst, ai->qname);
	dns_b_puts(&dst, " IN ");
	if (ai->qtype) {
		dns_b_puts(&dst, dns_strtype(ai->qtype));
	} else if (ent->ai_family == AF_INET) {
		dns_b_puts(&dst, dns_strtype(DNS_T_A));
	} else if (ent->ai_family == AF_INET6) {
		dns_b_puts(&dst, dns_strtype(DNS_T_AAAA));
	} else {
		dns_b_puts(&dst, "0");
	}
	dns_b_puts(&dst, " ]\n");

	dns_b_puts(&dst, ".ai_family    = ");
	switch (ent->ai_family) {
		case AF_INET:
			dns_b_puts(&dst, "AF_INET");
			break;
		case AF_INET6:
			dns_b_puts(&dst, "AF_INET6");
			break;
		default:
			dns_b_fmtju(&dst, ent->ai_family, 0);
			break;
	}
	dns_b_putc(&dst, '\n');

	dns_b_puts(&dst, ".ai_socktype  = ");
	switch (ent->ai_socktype) {
		case SOCK_STREAM:
			dns_b_puts(&dst, "SOCK_STREAM");
			break;
		case SOCK_DGRAM:
			dns_b_puts(&dst, "SOCK_DGRAM");
			break;
		default:
			dns_b_fmtju(&dst, ent->ai_socktype, 0);
			break;
	}
	dns_b_putc(&dst, '\n');

	dns_inet_ntop(dns_sa_family(ent->ai_addr), dns_sa_addr(dns_sa_family(ent->ai_addr), ent->ai_addr, NULL), addr,
	              sizeof addr);
	dns_b_puts(&dst, ".ai_addr      = [");
	dns_b_puts(&dst, addr);
	dns_b_puts(&dst, "]:");
	dns_b_fmtju(&dst, ntohs(*dns_sa_port(dns_sa_family(ent->ai_addr), ent->ai_addr)), 0);
	dns_b_putc(&dst, '\n');

	dns_b_puts(&dst, ".ai_canonname = ");
	dns_b_puts(&dst, (ent->ai_canonname) ? ent->ai_canonname : "[NULL]");
	dns_b_putc(&dst, '\n');

	return dns_b_strllen(&dst);
} /* dns_ai_print() */

const struct dns_stat *dns_ai_stat(struct dns_addrinfo *ai) {
	return (ai->res) ? dns_res_stat(ai->res) : &ai->st;
} /* dns_ai_stat() */

/*
 * M I S C E L L A N E O U S  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

static const struct {
	char name[16];
	enum dns_section type;
} dns_sections[] = {
    {"QUESTION", DNS_S_QUESTION},   {"QD", DNS_S_QUESTION},  {"ANSWER", DNS_S_ANSWER},         {"AN", DNS_S_ANSWER},
    {"AUTHORITY", DNS_S_AUTHORITY}, {"NS", DNS_S_AUTHORITY}, {"ADDITIONAL", DNS_S_ADDITIONAL}, {"AR", DNS_S_ADDITIONAL},
};

const char *(dns_strsection)(enum dns_section section, void *_dst, size_t lim) {
	struct dns_buf dst = DNS_B_INTO(_dst, lim);
	unsigned i;

	for (i = 0; i < lengthof(dns_sections); i++) {
		if (dns_sections[i].type & section) {
			dns_b_puts(&dst, dns_sections[i].name);
			section &= ~dns_sections[i].type;
			if (section) dns_b_putc(&dst, '|');
		}
	}

	if (section || dst.p == dst.base) dns_b_fmtju(&dst, (0xffff & section), 0);

	return dns_b_tostring(&dst);
} /* dns_strsection() */

enum dns_section dns_isection(const char *src) {
	enum dns_section section = 0;
	char sbuf[128];
	char *name, *next;
	unsigned i;

	dns_strlcpy(sbuf, src, sizeof sbuf);
	next = sbuf;

	while ((name = dns_strsep(&next, "|+, \t"))) {
		for (i = 0; i < lengthof(dns_sections); i++) {
			if (!strcasecmp(dns_sections[i].name, name)) {
				section |= dns_sections[i].type;
				break;
			}
		}
	}

	return section;
} /* dns_isection() */

static const struct {
	char name[8];
	enum dns_class type;
} dns_classes[] = {
    {"IN", DNS_C_IN},
};

const char *(dns_strclass)(enum dns_class type, void *_dst, size_t lim) {
	struct dns_buf dst = DNS_B_INTO(_dst, lim);
	unsigned i;

	for (i = 0; i < lengthof(dns_classes); i++) {
		if (dns_classes[i].type == type) {
			dns_b_puts(&dst, dns_classes[i].name);
			break;
		}
	}

	if (dst.p == dst.base) dns_b_fmtju(&dst, (0xffff & type), 0);

	return dns_b_tostring(&dst);
} /* dns_strclass() */

enum dns_class dns_iclass(const char *name) {
	unsigned i, class;

	for (i = 0; i < lengthof(dns_classes); i++) {
		if (!strcasecmp(dns_classes[i].name, name)) return dns_classes[i].type;
	}

	class = 0;
	while (dns_isdigit(*name)) {
		class *= 10;
		class += *name++ - '0';
	}

	return DNS_PP_MIN(class, 0xffff);
} /* dns_iclass() */

const char *(dns_strtype)(enum dns_type type, void *_dst, size_t lim) {
	struct dns_buf dst = DNS_B_INTO(_dst, lim);
	unsigned i;

	for (i = 0; i < lengthof(dns_rrtypes); i++) {
		if (dns_rrtypes[i].type == type) {
			dns_b_puts(&dst, dns_rrtypes[i].name);
			break;
		}
	}

	if (dst.p == dst.base) dns_b_fmtju(&dst, (0xffff & type), 0);

	return dns_b_tostring(&dst);
} /* dns_strtype() */

enum dns_type dns_itype(const char *name) {
	unsigned i, type;

	for (i = 0; i < lengthof(dns_rrtypes); i++) {
		if (!strcasecmp(dns_rrtypes[i].name, name)) return dns_rrtypes[i].type;
	}

	type = 0;
	while (dns_isdigit(*name)) {
		type *= 10;
		type += *name++ - '0';
	}

	return DNS_PP_MIN(type, 0xffff);
} /* dns_itype() */

static char dns_opcodes[16][16] = {
    [DNS_OP_QUERY] = "QUERY",   [DNS_OP_IQUERY] = "IQUERY", [DNS_OP_STATUS] = "STATUS",
    [DNS_OP_NOTIFY] = "NOTIFY", [DNS_OP_UPDATE] = "UPDATE",
};

static const char *dns__strcode(int code, volatile char *dst, size_t lim) {
	char _tmp[48] = "";
	struct dns_buf tmp;
	size_t p;

	assert(lim > 0);
	dns_b_fmtju(dns_b_into(&tmp, _tmp, DNS_PP_MIN(sizeof _tmp, lim - 1)), code, 0);

	/* copy downwards so first byte is copied last (see below) */
	p = (size_t)(tmp.p - tmp.base);
	dst[p] = '\0';
	while (p--)
		dst[p] = _tmp[p];

	return (const char *)dst;
}

const char *dns_stropcode(enum dns_opcode opcode) {
	opcode = (unsigned)opcode % lengthof(dns_opcodes);

	if ('\0' == dns_opcodes[opcode][0]) return dns__strcode(opcode, dns_opcodes[opcode], sizeof dns_opcodes[opcode]);

	return dns_opcodes[opcode];
} /* dns_stropcode() */

enum dns_opcode dns_iopcode(const char *name) {
	unsigned opcode;

	for (opcode = 0; opcode < lengthof(dns_opcodes); opcode++) {
		if (!strcasecmp(name, dns_opcodes[opcode])) return opcode;
	}

	opcode = 0;
	while (dns_isdigit(*name)) {
		opcode *= 10;
		opcode += *name++ - '0';
	}

	return DNS_PP_MIN(opcode, 0x0f);
} /* dns_iopcode() */

static char dns_rcodes[32][16] = {
    [DNS_RC_NOERROR] = "NOERROR",
    [DNS_RC_FORMERR] = "FORMERR",
    [DNS_RC_SERVFAIL] = "SERVFAIL",
    [DNS_RC_NXDOMAIN] = "NXDOMAIN",
    [DNS_RC_NOTIMP] = "NOTIMP",
    [DNS_RC_REFUSED] = "REFUSED",
    [DNS_RC_YXDOMAIN] = "YXDOMAIN",
    [DNS_RC_YXRRSET] = "YXRRSET",
    [DNS_RC_NXRRSET] = "NXRRSET",
    [DNS_RC_NOTAUTH] = "NOTAUTH",
    [DNS_RC_NOTZONE] = "NOTZONE",
    /* EDNS(0) extended RCODEs ... */
    [DNS_RC_BADVERS] = "BADVERS",
};

const char *dns_strrcode(enum dns_rcode rcode) {
	rcode = (unsigned)rcode % lengthof(dns_rcodes);

	if ('\0' == dns_rcodes[rcode][0]) return dns__strcode(rcode, dns_rcodes[rcode], sizeof dns_rcodes[rcode]);

	return dns_rcodes[rcode];
} /* dns_strrcode() */

enum dns_rcode dns_ircode(const char *name) {
	unsigned rcode;

	for (rcode = 0; rcode < lengthof(dns_rcodes); rcode++) {
		if (!strcasecmp(name, dns_rcodes[rcode])) return rcode;
	}

	rcode = 0;
	while (dns_isdigit(*name)) {
		rcode *= 10;
		rcode += *name++ - '0';
	}

	return DNS_PP_MIN(rcode, 0xfff);
} /* dns_ircode() */

/*
 * C O M M A N D - L I N E / R E G R E S S I O N  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
#if DNS_MAIN

#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>

#include <ctype.h>

#if _WIN32
#include <getopt.h>
#endif

#if !_WIN32
#include <err.h>
#endif

struct {
	struct {
		const char *path[8];
		unsigned count;
	} resconf, nssconf, hosts, cache;

	const char *qname;
	enum dns_type qtype;

	int (*sort)();

	int verbose;
} MAIN = {
    .sort = &dns_rr_i_packet,
};

static void hexdump(const unsigned char *src, size_t len, FILE *fp) {
	static const unsigned char hex[] = "0123456789abcdef";
	static const unsigned char tmpl[] = "                                                    |                |\n";
	unsigned char ln[sizeof tmpl];
	const unsigned char *sp, *se;
	unsigned char *h, *g;
	unsigned i, n;

	sp = src;
	se = sp + len;

	while (sp < se) {
		memcpy(ln, tmpl, sizeof ln);

		h = &ln[2];
		g = &ln[53];

		for (n = 0; n < 2; n++) {
			for (i = 0; i < 8 && se - sp > 0; i++, sp++) {
				h[0] = hex[0x0f & (*sp >> 4)];
				h[1] = hex[0x0f & (*sp >> 0)];
				h += 3;

				*g++ = (isgraph(*sp)) ? *sp : '.';
			}

			h++;
		}

		fputs((char *)ln, fp);
	}

	return /* void */;
} /* hexdump() */

DNS_NORETURN static void panic(const char *fmt, ...) {
	va_list ap;

	va_start(ap, fmt);

#if _WIN32
	vfprintf(stderr, fmt, ap);

	exit(EXIT_FAILURE);
#else
	verrx(EXIT_FAILURE, fmt, ap);
#endif
} /* panic() */

#define panic_(fn, ln, fmt, ...) panic(fmt "%0s", (fn), (ln), __VA_ARGS__)
#define panic(...) panic_(__func__, __LINE__, "(%s:%d) " __VA_ARGS__, "")

static void *grow(unsigned char *p, size_t size) {
	void *tmp;

	if (!(tmp = realloc(p, size))) panic("realloc(%" PRIuZ "): %s", size, dns_strerror(errno));

	return tmp;
} /* grow() */

static size_t add(size_t a, size_t b) {
	if (~a < b) panic("%" PRIuZ " + %" PRIuZ ": integer overflow", a, b);

	return a + b;
} /* add() */

static size_t append(unsigned char **dst, size_t osize, const void *src, size_t len) {
	size_t size = add(osize, len);

	*dst = grow(*dst, size);
	memcpy(*dst + osize, src, len);

	return size;
} /* append() */

static size_t slurp(unsigned char **dst, size_t osize, FILE *fp, const char *path) {
	size_t size = osize;
	unsigned char buf[1024];
	size_t count;

	while ((count = fread(buf, 1, sizeof buf, fp)))
		size = append(dst, size, buf, count);

	if (ferror(fp)) panic("%s: %s", path, dns_strerror(errno));

	return size;
} /* slurp() */

static struct dns_resolv_conf *resconf(void) {
	static struct dns_resolv_conf *resconf;
	const char *path;
	unsigned i;
	int error;

	if (resconf) return resconf;

	if (!(resconf = dns_resconf_open(&error))) panic("dns_resconf_open: %s", dns_strerror(error));

	if (!MAIN.resconf.count) MAIN.resconf.path[MAIN.resconf.count++] = "/etc/resolv.conf";

	for (i = 0; i < MAIN.resconf.count; i++) {
		path = MAIN.resconf.path[i];

		if (0 == strcmp(path, "-")) error = dns_resconf_loadfile(resconf, stdin);
		else error = dns_resconf_loadpath(resconf, path);

		if (error) panic("%s: %s", path, dns_strerror(error));
	}

	for (i = 0; i < MAIN.nssconf.count; i++) {
		path = MAIN.nssconf.path[i];

		if (0 == strcmp(path, "-")) error = dns_nssconf_loadfile(resconf, stdin);
		else error = dns_nssconf_loadpath(resconf, path);

		if (error) panic("%s: %s", path, dns_strerror(error));
	}

	if (!MAIN.nssconf.count) {
		path = "/etc/nsswitch.conf";

		if (!(error = dns_nssconf_loadpath(resconf, path))) MAIN.nssconf.path[MAIN.nssconf.count++] = path;
		else if (error != ENOENT) panic("%s: %s", path, dns_strerror(error));
	}

	return resconf;
} /* resconf() */

static struct dns_hosts *hosts(void) {
	static struct dns_hosts *hosts;
	const char *path;
	unsigned i;
	int error;

	if (hosts) return hosts;

	if (!MAIN.hosts.count) {
		MAIN.hosts.path[MAIN.hosts.count++] = "/etc/hosts";

		/* Explicitly test dns_hosts_local() */
		if (!(hosts = dns_hosts_local(&error))) panic("%s: %s", "/etc/hosts", dns_strerror(error));

		return hosts;
	}

	if (!(hosts = dns_hosts_open(&error))) panic("dns_hosts_open: %s", dns_strerror(error));

	for (i = 0; i < MAIN.hosts.count; i++) {
		path = MAIN.hosts.path[i];

		if (0 == strcmp(path, "-")) error = dns_hosts_loadfile(hosts, stdin);
		else error = dns_hosts_loadpath(hosts, path);

		if (error) panic("%s: %s", path, dns_strerror(error));
	}

	return hosts;
} /* hosts() */

#if DNS_CACHE
#include "cache.h"

static struct dns_cache *cache(void) {
	static struct cache *cache;
	const char *path;
	unsigned i;
	int error;

	if (cache) return cache_resi(cache);
	if (!MAIN.cache.count) return NULL;

	if (!(cache = cache_open(&error))) panic("%s: %s", MAIN.cache.path[0], dns_strerror(error));

	for (i = 0; i < MAIN.cache.count; i++) {
		path = MAIN.cache.path[i];

		if (!strcmp(path, "-")) {
			if ((error = cache_loadfile(cache, stdin, NULL, 0))) panic("%s: %s", path, dns_strerror(error));
		} else if ((error = cache_loadpath(cache, path, NULL, 0))) panic("%s: %s", path, dns_strerror(error));
	}

	return cache_resi(cache);
} /* cache() */
#else
static struct dns_cache *cache(void) {
	return NULL;
}
#endif

static void print_packet(struct dns_packet *P, FILE *fp) {
	dns_p_dump3(P, dns_rr_i_new(P, .sort = MAIN.sort), fp);

	if (MAIN.verbose > 2) hexdump(P->data, P->end, fp);
} /* print_packet() */

static int parse_packet(int argc DNS_NOTUSED, char *argv[] DNS_NOTUSED) {
	struct dns_packet *P = dns_p_new(512);
	struct dns_packet *Q = dns_p_new(512);
	enum dns_section section;
	struct dns_rr rr;
	int error;
	union dns_any any;
	char pretty[sizeof any * 2];
	size_t len;

	P->end = fread(P->data, 1, P->size, stdin);

	fputs(";; [HEADER]\n", stdout);
	fprintf(stdout, ";;     qr : %s(%d)\n", (dns_header(P)->qr) ? "RESPONSE" : "QUERY", dns_header(P)->qr);
	fprintf(stdout, ";; opcode : %s(%d)\n", dns_stropcode(dns_header(P)->opcode), dns_header(P)->opcode);
	fprintf(stdout, ";;     aa : %s(%d)\n", (dns_header(P)->aa) ? "AUTHORITATIVE" : "NON-AUTHORITATIVE",
	        dns_header(P)->aa);
	fprintf(stdout, ";;     tc : %s(%d)\n", (dns_header(P)->tc) ? "TRUNCATED" : "NOT-TRUNCATED", dns_header(P)->tc);
	fprintf(stdout, ";;     rd : %s(%d)\n", (dns_header(P)->rd) ? "RECURSION-DESIRED" : "RECURSION-NOT-DESIRED",
	        dns_header(P)->rd);
	fprintf(stdout, ";;     ra : %s(%d)\n", (dns_header(P)->ra) ? "RECURSION-ALLOWED" : "RECURSION-NOT-ALLOWED",
	        dns_header(P)->ra);
	fprintf(stdout, ";;  rcode : %s(%d)\n", dns_strrcode(dns_p_rcode(P)), dns_p_rcode(P));

	section = 0;

	dns_rr_foreach(&rr, P, .sort = MAIN.sort) {
		if (section != rr.section)
			fprintf(stdout, "\n;; [%s:%d]\n", dns_strsection(rr.section), dns_p_count(P, rr.section));

		if ((len = dns_rr_print(pretty, sizeof pretty, &rr, P, &error))) fprintf(stdout, "%s\n", pretty);

		dns_rr_copy(Q, &rr, P);

		section = rr.section;
	}

	fputs("; ; ; ; ; ; ; ;\n\n", stdout);

	section = 0;

#if 0
	dns_rr_foreach(&rr, Q, .name = "ns8.yahoo.com.") {
#else
	struct dns_rr rrset[32];
	struct dns_rr_i *rri = dns_rr_i_new(Q, .name = dns_d_new("ns8.yahoo.com", DNS_D_ANCHOR), .sort = MAIN.sort);
	unsigned rrcount = dns_rr_grep(rrset, lengthof(rrset), rri, Q, &error);

	for (unsigned i = 0; i < rrcount; i++) {
		rr = rrset[i];
#endif
		if (section != rr.section)
			fprintf(stdout, "\n;; [%s:%d]\n", dns_strsection(rr.section), dns_p_count(Q, rr.section));

		if ((len = dns_rr_print(pretty, sizeof pretty, &rr, Q, &error))) fprintf(stdout, "%s\n", pretty);

		section = rr.section;
	}

	if (MAIN.verbose > 1) {
		fprintf(stderr, "orig:%" PRIuZ "\n", P->end);
		hexdump(P->data, P->end, stdout);

		fprintf(stderr, "copy:%" PRIuZ "\n", Q->end);
		hexdump(Q->data, Q->end, stdout);
	}

	return 0;
} /* parse_packet() */

static int parse_domain(int argc, char *argv[]) {
	char *dn;

	dn = (argc > 1) ? argv[1] : "f.l.google.com";

	printf("[%s]\n", dn);

	dn = dns_d_new(dn);

	do {
		puts(dn);
	} while (dns_d_cleave(dn, strlen(dn) + 1, dn, strlen(dn)));

	return 0;
} /* parse_domain() */

static int trim_domain(int argc, char **argv) {
	for (argc--, argv++; argc > 0; argc--, argv++) {
		char name[DNS_D_MAXNAME + 1];

		dns_d_trim(name, sizeof name, *argv, strlen(*argv), DNS_D_ANCHOR);

		puts(name);
	}

	return 0;
} /* trim_domain() */

static int expand_domain(int argc, char *argv[]) {
	unsigned short rp = 0;
	unsigned char *src = NULL;
	unsigned char *dst;
	struct dns_packet *pkt;
	size_t lim = 0, len;
	int error;

	if (argc > 1) rp = atoi(argv[1]);

	len = slurp(&src, 0, stdin, "-");

	if (!(pkt = dns_p_make(len, &error))) panic("malloc(%" PRIuZ "): %s", len, dns_strerror(error));

	memcpy(pkt->data, src, len);
	pkt->end = len;

	lim = 1;
	dst = grow(NULL, lim);

	while (lim <= (len = dns_d_expand(dst, lim, rp, pkt, &error))) {
		lim = add(len, 1);
		dst = grow(dst, lim);
	}

	if (!len) panic("expand: %s", dns_strerror(error));

	fwrite(dst, 1, len, stdout);
	fflush(stdout);

	free(src);
	free(dst);
	free(pkt);

	return 0;
} /* expand_domain() */

static int show_resconf(int argc DNS_NOTUSED, char *argv[] DNS_NOTUSED) {
	unsigned i;

	resconf(); /* load it */

	fputs("; SOURCES\n", stdout);

	for (i = 0; i < MAIN.resconf.count; i++)
		fprintf(stdout, ";   %s\n", MAIN.resconf.path[i]);

	for (i = 0; i < MAIN.nssconf.count; i++)
		fprintf(stdout, ";   %s\n", MAIN.nssconf.path[i]);

	fputs(";\n", stdout);

	dns_resconf_dump(resconf(), stdout);

	return 0;
} /* show_resconf() */

static int show_nssconf(int argc DNS_NOTUSED, char *argv[] DNS_NOTUSED) {
	unsigned i;

	resconf();

	fputs("# SOURCES\n", stdout);

	for (i = 0; i < MAIN.resconf.count; i++)
		fprintf(stdout, "#   %s\n", MAIN.resconf.path[i]);

	for (i = 0; i < MAIN.nssconf.count; i++)
		fprintf(stdout, "#   %s\n", MAIN.nssconf.path[i]);

	fputs("#\n", stdout);

	dns_nssconf_dump(resconf(), stdout);

	return 0;
} /* show_nssconf() */

static int show_hosts(int argc DNS_NOTUSED, char *argv[] DNS_NOTUSED) {
	unsigned i;

	hosts();

	fputs("# SOURCES\n", stdout);

	for (i = 0; i < MAIN.hosts.count; i++)
		fprintf(stdout, "#   %s\n", MAIN.hosts.path[i]);

	fputs("#\n", stdout);

	dns_hosts_dump(hosts(), stdout);

	return 0;
} /* show_hosts() */

static int query_hosts(int argc, char *argv[]) {
	struct dns_packet *Q = dns_p_new(512);
	struct dns_packet *A;
	char qname[DNS_D_MAXNAME + 1];
	size_t qlen;
	int error;

	if (!MAIN.qname) MAIN.qname = (argc > 1) ? argv[1] : "localhost";
	if (!MAIN.qtype) MAIN.qtype = DNS_T_A;

	hosts();

	if (MAIN.qtype == DNS_T_PTR && !strstr(MAIN.qname, "arpa")) {
		union {
			struct in_addr a;
			struct in6_addr a6;
		} addr;
		int af = (strchr(MAIN.qname, ':')) ? AF_INET6 : AF_INET;

		if ((error = dns_pton(af, MAIN.qname, &addr))) panic("%s: %s", MAIN.qname, dns_strerror(error));

		qlen = dns_ptr_qname(qname, sizeof qname, af, &addr);
	} else qlen = dns_strlcpy(qname, MAIN.qname, sizeof qname);

	if ((error = dns_p_push(Q, DNS_S_QD, qname, qlen, MAIN.qtype, DNS_C_IN, 0, 0)))
		panic("%s: %s", qname, dns_strerror(error));

	if (!(A = dns_hosts_query(hosts(), Q, &error))) panic("%s: %s", qname, dns_strerror(error));

	print_packet(A, stdout);

	free(A);

	return 0;
} /* query_hosts() */

static int search_list(int argc, char *argv[]) {
	const char *qname = (argc > 1) ? argv[1] : "f.l.google.com";
	unsigned long i = 0;
	char name[DNS_D_MAXNAME + 1];

	printf("[%s]\n", qname);

	while (dns_resconf_search(name, sizeof name, qname, strlen(qname), resconf(), &i))
		puts(name);

	return 0;
} /* search_list() */

static int permute_set(int argc, char *argv[]) {
	unsigned lo, hi, i;
	struct dns_k_permutor p;

	hi = (--argc > 0) ? atoi(argv[argc]) : 8;
	lo = (--argc > 0) ? atoi(argv[argc]) : 0;

	fprintf(stderr, "[%u .. %u]\n", lo, hi);

	dns_k_permutor_init(&p, lo, hi);

	for (i = lo; i <= hi; i++)
		fprintf(stdout, "%u\n", dns_k_permutor_step(&p));
	//		printf("%u -> %u -> %u\n", i, dns_k_permutor_E(&p, i), dns_k_permutor_D(&p, dns_k_permutor_E(&p, i)));

	return 0;
} /* permute_set() */

static int shuffle_16(int argc, char *argv[]) {
	unsigned n, r;

	if (--argc > 0) {
		n = 0xffff & atoi(argv[argc]);
		r = (--argc > 0) ? (unsigned)atoi(argv[argc]) : dns_random();

		fprintf(stdout, "%hu\n", dns_k_shuffle16(n, r));
	} else {
		r = dns_random();

		for (n = 0; n < 65536; n++)
			fprintf(stdout, "%hu\n", dns_k_shuffle16(n, r));
	}

	return 0;
} /* shuffle_16() */

static int dump_random(int argc, char *argv[]) {
	unsigned char b[32];
	unsigned i, j, n, r;

	n = (argc > 1) ? atoi(argv[1]) : 32;

	while (n) {
		i = 0;

		do {
			r = dns_random();

			for (j = 0; j < sizeof r && i < n && i < sizeof b; i++, j++) {
				b[i] = 0xff & r;
				r >>= 8;
			}
		} while (i < n && i < sizeof b);

		hexdump(b, i, stdout);

		n -= i;
	}

	return 0;
} /* dump_random() */

static int send_query(int argc, char *argv[]) {
	struct dns_packet *A, *Q = dns_p_new(512);
	char host[INET6_ADDRSTRLEN + 1];
	struct sockaddr_storage ss;
	struct dns_socket *so;
	int error, type;

	if (argc > 1) {
		ss.ss_family = (strchr(argv[1], ':')) ? AF_INET6 : AF_INET;

		if ((error = dns_pton(ss.ss_family, argv[1], dns_sa_addr(ss.ss_family, &ss, NULL))))
			panic("%s: %s", argv[1], dns_strerror(error));

		*dns_sa_port(ss.ss_family, &ss) = htons(53);
	} else memcpy(&ss, &resconf()->nameserver[0], dns_sa_len(&resconf()->nameserver[0]));

	if (!dns_inet_ntop(ss.ss_family, dns_sa_addr(ss.ss_family, &ss, NULL), host, sizeof host))
		panic("bad host address, or none provided");

	if (!MAIN.qname) MAIN.qname = "ipv6.google.com";
	if (!MAIN.qtype) MAIN.qtype = DNS_T_AAAA;

	if ((error = dns_p_push(Q, DNS_S_QD, MAIN.qname, strlen(MAIN.qname), MAIN.qtype, DNS_C_IN, 0, 0)))
		panic("dns_p_push: %s", dns_strerror(error));

	dns_header(Q)->rd = 1;

	if (strstr(argv[0], "udp")) type = SOCK_DGRAM;
	else if (strstr(argv[0], "tcp")) type = SOCK_STREAM;
	else type = dns_res_tcp2type(resconf()->options.tcp);

	fprintf(stderr, "querying %s for %s IN %s\n", host, MAIN.qname, dns_strtype(MAIN.qtype));

	if (!(so = dns_so_open((struct sockaddr *)&resconf()->iface, type, dns_opts(), &error)))
		panic("dns_so_open: %s", dns_strerror(error));

	while (!(A = dns_so_query(so, Q, (struct sockaddr *)&ss, &error))) {
		if (error != DNS_EAGAIN) panic("dns_so_query: %s (%d)", dns_strerror(error), error);
		if (dns_so_elapsed(so) > 10) panic("query timed-out");

		dns_so_poll(so, 1);
	}

	print_packet(A, stdout);

	dns_so_close(so);

	return 0;
} /* send_query() */

static int print_arpa(int argc, char *argv[]) {
	const char *ip = (argc > 1) ? argv[1] : "::1";
	int af = (strchr(ip, ':')) ? AF_INET6 : AF_INET;
	union {
		struct in_addr a4;
		struct in6_addr a6;
	} addr;
	char host[DNS_D_MAXNAME + 1];

	if (1 != dns_inet_pton(af, ip, &addr) || 0 == dns_ptr_qname(host, sizeof host, af, &addr))
		panic("%s: invalid address", ip);

	fprintf(stdout, "%s\n", host);

	return 0;
} /* print_arpa() */

static int show_hints(int argc, char *argv[]) {
	struct dns_hints *(*load)(struct dns_resolv_conf *, int *);
	const char *which, *how, *who;
	struct dns_hints *hints;
	int error;

	which = (argc > 1) ? argv[1] : "local";
	how = (argc > 2) ? argv[2] : "plain";
	who = (argc > 3) ? argv[3] : "google.com";

	load = (0 == strcmp(which, "local")) ? &dns_hints_local : &dns_hints_root;

	if (!(hints = load(resconf(), &error))) panic("%s: %s", argv[0], dns_strerror(error));

	if (0 == strcmp(how, "plain")) {
		dns_hints_dump(hints, stdout);
	} else {
		struct dns_packet *query, *answer;

		query = dns_p_new(512);

		if ((error = dns_p_push(query, DNS_S_QUESTION, who, strlen(who), DNS_T_A, DNS_C_IN, 0, 0)))
			panic("%s: %s", who, dns_strerror(error));

		if (!(answer = dns_hints_query(hints, query, &error))) panic("%s: %s", who, dns_strerror(error));

		print_packet(answer, stdout);

		free(answer);
	}

	dns_hints_close(hints);

	return 0;
} /* show_hints() */

static int resolve_query(int argc DNS_NOTUSED, char *argv[]) {
	_Bool recurse = !!strstr(argv[0], "recurse");
	struct dns_hints *(*hints)() = (recurse) ? &dns_hints_root : &dns_hints_local;
	struct dns_resolver *R;
	struct dns_packet *ans;
	const struct dns_stat *st;
	int error;

	if (!MAIN.qname) MAIN.qname = "www.google.com";
	if (!MAIN.qtype) MAIN.qtype = DNS_T_A;

	resconf()->options.recurse = recurse;

	if (!(R = dns_res_open(resconf(), hosts(), dns_hints_mortal(hints(resconf(), &error)), cache(), dns_opts(),
	                       &error)))
		panic("%s: %s", MAIN.qname, dns_strerror(error));

	if ((error = dns_res_submit(R, MAIN.qname, MAIN.qtype, DNS_C_IN))) panic("%s: %s", MAIN.qname, dns_strerror(error));

	while ((error = dns_res_check(R))) {
		if (error != DNS_EAGAIN) panic("dns_res_check: %s (%d)", dns_strerror(error), error);
		if (dns_res_elapsed(R) > 30) panic("query timed-out");

		dns_res_poll(R, 1);
	}

	ans = dns_res_fetch(R, &error);
	print_packet(ans, stdout);
	free(ans);

	st = dns_res_stat(R);
	putchar('\n');
	printf(";; queries:  %" PRIuZ "\n", st->queries);
	printf(";; udp sent: %" PRIuZ " in %" PRIuZ " bytes\n", st->udp.sent.count, st->udp.sent.bytes);
	printf(";; udp rcvd: %" PRIuZ " in %" PRIuZ " bytes\n", st->udp.rcvd.count, st->udp.rcvd.bytes);
	printf(";; tcp sent: %" PRIuZ " in %" PRIuZ " bytes\n", st->tcp.sent.count, st->tcp.sent.bytes);
	printf(";; tcp rcvd: %" PRIuZ " in %" PRIuZ " bytes\n", st->tcp.rcvd.count, st->tcp.rcvd.bytes);

	dns_res_close(R);

	return 0;
} /* resolve_query() */

static int resolve_addrinfo(int argc DNS_NOTUSED, char *argv[]) {
	_Bool recurse = !!strstr(argv[0], "recurse");
	struct dns_hints *(*hints)() = (recurse) ? &dns_hints_root : &dns_hints_local;
	struct dns_resolver *res = NULL;
	struct dns_addrinfo *ai = NULL;
	struct addrinfo ai_hints = {.ai_family = PF_UNSPEC, .ai_socktype = SOCK_STREAM, .ai_flags = AI_CANONNAME};
	struct addrinfo *ent;
	char pretty[512];
	int error;

	if (!MAIN.qname) MAIN.qname = "www.google.com";
	/* NB: MAIN.qtype of 0 means obey hints.ai_family */

	resconf()->options.recurse = recurse;

	if (!(res = dns_res_open(resconf(), hosts(), dns_hints_mortal(hints(resconf(), &error)), cache(), dns_opts(),
	                         &error)))
		panic("%s: %s", MAIN.qname, dns_strerror(error));

	if (!(ai = dns_ai_open(MAIN.qname, "80", MAIN.qtype, &ai_hints, res, &error)))
		panic("%s: %s", MAIN.qname, dns_strerror(error));

	do {
		switch (error = dns_ai_nextent(&ent, ai)) {
			case 0:
				dns_ai_print(pretty, sizeof pretty, ent, ai);

				fputs(pretty, stdout);

				free(ent);

				break;
			case ENOENT:
				break;
			case DNS_EAGAIN:
				if (dns_ai_elapsed(ai) > 30) panic("query timed-out");

				dns_ai_poll(ai, 1);

				break;
			default:
				panic("dns_ai_nextent: %s (%d)", dns_strerror(error), error);
		}
	} while (error != ENOENT);

	dns_res_close(res);
	dns_ai_close(ai);

	return 0;
} /* resolve_addrinfo() */

static int echo_port(int argc DNS_NOTUSED, char *argv[] DNS_NOTUSED) {
	union {
		struct sockaddr sa;
		struct sockaddr_in sin;
	} port;
	int fd;

	memset(&port, 0, sizeof port);
	port.sin.sin_family = AF_INET;
	port.sin.sin_port = htons(5354);
	port.sin.sin_addr.s_addr = inet_addr("127.0.0.1");

	if (-1 == (fd = socket(PF_INET, SOCK_DGRAM, 0))) panic("socket: %s", strerror(errno));

	if (0 != bind(fd, &port.sa, sizeof port.sa)) panic("127.0.0.1:5353: %s", dns_strerror(errno));

	for (;;) {
		struct dns_packet *pkt = dns_p_new(512);
		struct sockaddr_storage ss;
		socklen_t slen = sizeof ss;
		ssize_t count;
#if defined(MSG_WAITALL) /* MinGW issue */
		int rflags = MSG_WAITALL;
#else
		int rflags = 0;
#endif

		count = recvfrom(fd, (char *)pkt->data, pkt->size, rflags, (struct sockaddr *)&ss, &slen);

		if (!count || count < 0) panic("recvfrom: %s", strerror(errno));

		pkt->end = count;

		dns_p_dump(pkt, stdout);

		(void)sendto(fd, (char *)pkt->data, pkt->end, 0, (struct sockaddr *)&ss, slen);
	}

	return 0;
} /* echo_port() */

static int isection(int argc, char *argv[]) {
	const char *name = (argc > 1) ? argv[1] : "";
	int type;

	type = dns_isection(name);
	name = dns_strsection(type);

	printf("%s (%d)\n", name, type);

	return 0;
} /* isection() */

static int iclass(int argc, char *argv[]) {
	const char *name = (argc > 1) ? argv[1] : "";
	int type;

	type = dns_iclass(name);
	name = dns_strclass(type);

	printf("%s (%d)\n", name, type);

	return 0;
} /* iclass() */

static int itype(int argc, char *argv[]) {
	const char *name = (argc > 1) ? argv[1] : "";
	int type;

	type = dns_itype(name);
	name = dns_strtype(type);

	printf("%s (%d)\n", name, type);

	return 0;
} /* itype() */

static int iopcode(int argc, char *argv[]) {
	const char *name = (argc > 1) ? argv[1] : "";
	int type;

	type = dns_iopcode(name);
	name = dns_stropcode(type);

	printf("%s (%d)\n", name, type);

	return 0;
} /* iopcode() */

static int ircode(int argc, char *argv[]) {
	const char *name = (argc > 1) ? argv[1] : "";
	int type;

	type = dns_ircode(name);
	name = dns_strrcode(type);

	printf("%s (%d)\n", name, type);

	return 0;
} /* ircode() */

#define SIZE1(x)                                                                                                       \
	{ DNS_PP_STRINGIFY(x), sizeof(x) }
#define SIZE2(x, ...) SIZE1(x), SIZE1(__VA_ARGS__)
#define SIZE3(x, ...) SIZE1(x), SIZE2(__VA_ARGS__)
#define SIZE4(x, ...) SIZE1(x), SIZE3(__VA_ARGS__)
#define SIZE(...) DNS_PP_CALL(DNS_PP_XPASTE(SIZE, DNS_PP_NARG(__VA_ARGS__)), __VA_ARGS__)

static int sizes(int argc DNS_NOTUSED, char *argv[] DNS_NOTUSED) {
	static const struct {
		const char *name;
		size_t size;
	} type[] = {SIZE(struct dns_header, struct dns_packet, struct dns_rr, struct dns_rr_i),
	            SIZE(struct dns_a, struct dns_aaaa, struct dns_mx, struct dns_ns),
	            SIZE(struct dns_cname, struct dns_soa, struct dns_ptr, struct dns_srv),
	            SIZE(struct dns_sshfp, struct dns_txt, union dns_any),
	            SIZE(struct dns_resolv_conf, struct dns_hosts, struct dns_hints, struct dns_hints_i),
	            SIZE(struct dns_options, struct dns_socket, struct dns_resolver, struct dns_addrinfo),
	            SIZE(struct dns_cache),
	            SIZE(size_t),
	            SIZE(void *),
	            SIZE(long)};
	unsigned i, max;

	for (i = 0, max = 0; i < lengthof(type); i++)
		max = DNS_PP_MAX(max, strlen(type[i].name));

	for (i = 0; i < lengthof(type); i++)
		printf("%*s : %" PRIuZ "\n", max, type[i].name, type[i].size);

	return 0;
} /* sizes() */

static const struct {
	const char *cmd;
	int (*run)();
	const char *help;
} cmds[] = {
    {"parse-packet", &parse_packet, "parse binary packet from stdin"},
    {"parse-domain", &parse_domain, "anchor and iteratively cleave domain"},
    {"trim-domain", &trim_domain, "trim and anchor domain name"},
    {"expand-domain", &expand_domain, "expand domain at offset NN in packet from stdin"},
    {"show-resconf", &show_resconf, "show resolv.conf data"},
    {"show-hosts", &show_hosts, "show hosts data"},
    {"show-nssconf", &show_nssconf, "show nsswitch.conf data"},
    {"query-hosts", &query_hosts, "query A, AAAA or PTR in hosts data"},
    {"search-list", &search_list, "generate query search list from domain"},
    {"permute-set", &permute_set, "generate random permutation -> (0 .. N or N .. M)"},
    {"shuffle-16", &shuffle_16, "simple 16-bit permutation"},
    {"dump-random", &dump_random, "generate random bytes"},
    {"send-query", &send_query, "send query to host"},
    {"send-query-udp", &send_query, "send udp query to host"},
    {"send-query-tcp", &send_query, "send tcp query to host"},
    {"print-arpa", &print_arpa, "print arpa. zone name of address"},
    {"show-hints", &show_hints, "print hints: show-hints [local|root] [plain|packet]"},
    {"resolve-stub", &resolve_query, "resolve as stub resolver"},
    {"resolve-recurse", &resolve_query, "resolve as recursive resolver"},
    {"addrinfo-stub", &resolve_addrinfo, "resolve through getaddrinfo clone"},
    {"addrinfo-recurse", &resolve_addrinfo, "resolve through getaddrinfo clone"},
    /*	{ "resolve-nameinfo",	&resolve_query,		"resolve as recursive resolver" }, */
    {"echo", &echo_port, "server echo mode, for nmap fuzzing"},
    {"isection", &isection, "parse section string"},
    {"iclass", &iclass, "parse class string"},
    {"itype", &itype, "parse type string"},
    {"iopcode", &iopcode, "parse opcode string"},
    {"ircode", &ircode, "parse rcode string"},
    {"sizes", &sizes, "print data structure sizes"},
};

static void print_usage(const char *progname, FILE *fp) {
	static const char *usage = " [OPTIONS] COMMAND [ARGS]\n"
	                           "  -c PATH   Path to resolv.conf\n"
	                           "  -n PATH   Path to nsswitch.conf\n"
	                           "  -l PATH   Path to local hosts\n"
	                           "  -z PATH   Path to zone cache\n"
	                           "  -q QNAME  Query name\n"
	                           "  -t QTYPE  Query type\n"
	                           "  -s HOW    Sort records\n"
	                           "  -v        Be more verbose (-vv show packets; -vvv hexdump packets)\n"
	                           "  -V        Print version info\n"
	                           "  -h        Print this usage message\n"
	                           "\n";
	unsigned i, n, m;

	fputs(progname, fp);
	fputs(usage, fp);

	for (i = 0, m = 0; i < lengthof(cmds); i++) {
		if (strlen(cmds[i].cmd) > m) m = strlen(cmds[i].cmd);
	}

	for (i = 0; i < lengthof(cmds); i++) {
		fprintf(fp, "  %s  ", cmds[i].cmd);

		for (n = strlen(cmds[i].cmd); n < m; n++)
			putc(' ', fp);

		fputs(cmds[i].help, fp);
		putc('\n', fp);
	}

	fputs("\nReport bugs to William Ahern <william@25thandClement.com>\n", fp);
} /* print_usage() */

static void print_version(const char *progname, FILE *fp) {
	fprintf(fp, "%s (dns.c) %.8X\n", progname, dns_v_rel());
	fprintf(fp, "vendor  %s\n", dns_vendor());
	fprintf(fp, "release %.8X\n", dns_v_rel());
	fprintf(fp, "abi     %.8X\n", dns_v_abi());
	fprintf(fp, "api     %.8X\n", dns_v_api());
} /* print_version() */

int main(int argc, char **argv) {
	extern int optind;
	extern char *optarg;
	const char *progname = argv[0];
	unsigned i;
	int ch;

	while (-1 != (ch = getopt(argc, argv, "q:t:c:n:l:z:s:vVh"))) {
		switch (ch) {
			case 'c':
				assert(MAIN.resconf.count < lengthof(MAIN.resconf.path));

				MAIN.resconf.path[MAIN.resconf.count++] = optarg;

				break;
			case 'n':
				assert(MAIN.nssconf.count < lengthof(MAIN.nssconf.path));

				MAIN.nssconf.path[MAIN.nssconf.count++] = optarg;

				break;
			case 'l':
				assert(MAIN.hosts.count < lengthof(MAIN.hosts.path));

				MAIN.hosts.path[MAIN.hosts.count++] = optarg;

				break;
			case 'z':
				assert(MAIN.cache.count < lengthof(MAIN.cache.path));

				MAIN.cache.path[MAIN.cache.count++] = optarg;

				break;
			case 'q':
				MAIN.qname = optarg;

				break;
			case 't':
				for (i = 0; i < lengthof(dns_rrtypes); i++) {
					if (0 == strcasecmp(dns_rrtypes[i].name, optarg)) {
						MAIN.qtype = dns_rrtypes[i].type;
						break;
					}
				}

				if (MAIN.qtype) break;

				for (i = 0; dns_isdigit(optarg[i]); i++) {
					MAIN.qtype *= 10;
					MAIN.qtype += optarg[i] - '0';
				}

				if (!MAIN.qtype) panic("%s: invalid query type", optarg);

				break;
			case 's':
				if (0 == strcasecmp(optarg, "packet")) MAIN.sort = &dns_rr_i_packet;
				else if (0 == strcasecmp(optarg, "shuffle")) MAIN.sort = &dns_rr_i_shuffle;
				else if (0 == strcasecmp(optarg, "order")) MAIN.sort = &dns_rr_i_order;
				else panic("%s: invalid sort method", optarg);

				break;
			case 'v':
				dns_debug = ++MAIN.verbose;

				break;
			case 'V':
				print_version(progname, stdout);

				return 0;
			case 'h':
				print_usage(progname, stdout);

				return 0;
			default:
				print_usage(progname, stderr);

				return EXIT_FAILURE;
		} /* switch() */
	}     /* while() */

	argc -= optind;
	argv += optind;

	for (i = 0; i < lengthof(cmds) && argv[0]; i++) {
		if (0 == strcmp(cmds[i].cmd, argv[0])) return cmds[i].run(argc, argv);
	}

	print_usage(progname, stderr);

	return EXIT_FAILURE;
} /* main() */

#endif /* DNS_MAIN */

/*
 * pop file-scoped compiler annotations
 */
#if __clang__
#pragma clang diagnostic pop
#elif DNS_GNUC_PREREQ(4, 6, 0)
#pragma GCC diagnostic pop
#endif
